I am not sure how you are using kōan practice right now so I will discuss it with you.
The Mind is neither large nor small; it is located neither within nor without. It should not be thought about by the mind nor be discussed by the mouth. Ordinarily, it is said that we use the Mind to transmit the Mind, or that we use the Mind to seal the Mind. Actually, however, in transmitting the Mind, there is really no Mind to receive or obtain; and in sealing the Mind, there is really no Mind to seal. If this is the case, then does the Mind exist or does it not exist? Actually, it cannot be said with certainty that the Mind either exists or does not exist, for it is Absolute Reality. This is expressed in the Chán Sect by the maxim: “If you open your mouth, you are wrong. If you give rise to a single thought, you are in error.” So, if you can quiet your thinking totally, all that remains is transparency and stillness.
The Mind is Buddha; Buddha is the Mind. All sentient beings and all Buddhas have the same Mind, which is without boundaries and clear like space, without name and form and is immeasurable.
What is your Original Face and what is Huàtóu? Your Original Face is without discrimination. Huàtóu is the Reality before the arising of a single thought. When this Mind is enlightened, it is the Buddha; but when it is confused, it remains only the mind of sentient beings. So sitting in Shikantaza is correct practice and the Huàtóu, “what is this?....don’t know……!” is used each time thinking arises during practice and we recognize it. Yet, correct Zen Practice is actually how do you keep your mind, moment after moment after moment. So, not just on the cushion, but each moment. When writing time, then just writing. When cooking time, just cooking. When wife comes home, then just husband mind. Also, when doing nothing time, just do nothing. So during sitting meditation we say that we sit in Shikantaza and when thinking arises we use our Huàtóu to return back to this present moment, not by naming “what is this” but by just using “don’t know” to return to a non-thinking state.
In answer to your question about studying the Dharma I’d like to give you some background on our direction of practice which is different from the Soto (Cáodòng) or even the Rinzai (Línjì) Schools. Sŏn Master Chinul who is the founder of our approach to practice was a Korean monk who worked to reform the monastic order and provide a rationale for Sŏn practice. Observing that the commercialization of monastic activities (in the form of fortune-telling, services for paying clients, and so on) had brought many into the order for questionable motives, he sought to create a reform group called the ‘concentration and wisdom society’, which found a home when he established the Sŏngwang Sa on Mt. Jögye. At the same time, he concerned himself with theoretical issues relating to the controversy between gradual and sudden enlightenment, and the relationship between meditative experience and doctrinal/textual studies. In the former case, he adopted the typology of the Chinese Chán and Huáyán master Tsung-mi, which advocated sudden enlightenment followed by a gradual deepening and cultivation as the norm. In order to serve this purpose, he proposed meditation on kōans as the best method of practice. As to the latter, he advised that Korean Sŏn not follow the example of the more extreme trends towards rejection of scriptural and doctrinal study exhibited by Chinese Chán, but that it keep the two together as an integrated whole. He was particularly interested in incorporating the Huáyán philosophy of the Chinese lay hermit Li T'ung-hsüan into Sŏn practice as its basis and rationale. Chinul produced many eminent and accomplished disciples, and is arguably one of the most influential monks in the history of Korean Buddhism.
So, studying is also a way where we can begin to digest our understanding of the Dharma. It isn’t important to understand it, it is just to study and over time we can digest it and the Dharma will eventually become our own. This is all the correct form of practicing in our school.
Student training involves leaning how to focus your attention, so that you might experience a before-thinking mind. This allows an experiential contact with your original nature and is sometimes called kensho (to perceive your true nature). Meditation, both seated and walking, various types of yoga and some types of martial arts are all useful in this training. If you are working on a particular kōan, or holding a huàtóu and you don't understand it, then not understanding is where you are right now. If you maintain a not understanding mind eventually your not knowing mind will become stronger and stronger. Once this not knowing and you become one, you will then be able to maintain the great question and have great doubt. When you can finally allow this not knowing to permeate all of your senses, then you will attain complete enlightenment. If you keep a small question, then small enlightenment is possible. There are many kinds of enlightenment; first enlightenment, second enlightenment, third enlightenment, and then finally, no enlightenment. No enlightenment is perfect enlightenment.
If you are creating something special in your life, then you will also have a problem understanding some aspect of kōan practice; so one use of kōan practice is to take away your opinion. If you can drop your opinion, it is then possible to manifest a mind that is clear like space. Furthermore, correct Zen practice shows up in your ability to respond to each situation correctly and meticulously. It also means that you must understand your correct job in this very moment. This means that moment–to–moment the correct relationship appears of itself. When kōan practice is correct, the moment–to–moment correct situation, correct function, and correct relationship will appear by itself.
If you hold your kōan too tightly, or become attached to your kōan, or want something from kōan practice, then you will end up with a big problem. Keeping your current kōan or “a don’t know mind,” moment after moment after moment without making anything, is by itself correct direction and correct life. The old-style kōans give you a great gift in the form of a question like: What is life? What is death? What is mind? What is this moment?
By Most Ven. Wonji Dharma - Reposted from Perceive Sound Zen Community 想音禪中心: A Letter to a Beginning Student