Primary thinking is desirable because by it we escape alienation and participate in reality; and can also attain to direct knowing by communion of thought - unmediated by language and communications.
In other words it is not the kind of thing that can be done as a technique, not practiced as a method; nor is it at all likely to be a frequent or lasting state - for the simple reason that we are seldom wholly aligned with God's purposes and providence.
(In other words; in this mortal life we cannot for long avoid sin - the turning-away from God's ongoing purposes - and sin blocks Final Participation.)
However; I think there are some things that might be helpful in attaining, while other things tend to inhibit, Final Participation.
Most (or all) of our normal everyday thinking is secondary, not primary; that is to say it is thinking driven (caused) by external stimuli or internal associations (as in dreams or clouded consciousness).
So, removing or reducing secondary thinking is probably helpful. For instance reducing external distractions.
And staying awake and alert, too.
As a first step, self-remembering may be valuable in setting us along the path: that is, recognizing "Me! Here! Now!"
Or, by making a deliberate effort to consider one's physical sensations - touch (feet pressing the ground, wind between the fingers etc.); vision - noticing surroundings that are normally taken for granted, such as the sky or small details; hearing - listening beyond the obvious to background and environmental sounds.
This may lead to an opening-out, a coming-to, an awakening of awareness simultaneously of the self and surroundings. Plus, especially, awareness of the presence of the Holy Ghost - everywher, invisible, but a person whom we can know.
Secondly, to allow the real, primary self to come to awareness - our conscious will can perceive and recognize that thinking that comes from the divine in us.
We are equipped (by God) to detect and know this.
So - we need to recognize "It is happening, Now!"
Thirdly, this is the time to recall that primary thinking is reality; by thinking thus we are participating in divine creation - and this is the source of direct knowing and genuine (genius-type) creativity.
This serves to validate what we are experiencing - to remind us that it is true, real and Good.
Of course, in practice, it is very easy to be thrown off track at any point, and to lose the actuality of primary thinking. For instance - we may take a passive, not-thinking, un-self-aware path - which leads us towards lower consciousness, less human and less divine. We may fall into a trance or asleep!
Much the same applies if our motivation becomes to seek blissful or exciting mental states, to use Final Participation as an 'analgesic' or escape from suffering - or to prolong the state of primary thinking for this kind of psychological-emotional reason.
Primary thinking is certainly rewarding - nothing more so- but as a by-product. If pleasurable gratification becomes the end and aim - then primary thinking ceases.
Or our superficial thinking may try to 'hijack' the primary thinking in order to attain some personal and selfish goal, to manipulate others or the world (as with some kind of 'black magic'). In which case we will instantly drop-out-from primary thinking down-into merely secondary and superficial mundane cognition.
Only when we are actually aligned-with divine creation and providence can we attain Final Participation - when it happens automatically. On the one hand, if we try to use it for some worldly purpose, the state ceases. But, by recognizing the validity and here-and-now presence of its happening; we can encourage its recurrence, and learn from the experience.