>>12787192I know this will probably sound like crankery but I just heard a neuroscientist talk about this on a recent podcast and he said he thinks a lot of people are sleeping on the possibility that you can actually do this. He thinks it's been underreported and that in some years it'll become much more common
I'd recommend listening to exactly what he says, but basically it's about optimizing levels of acetylcholine and dopamine (particularly acetylcholine), in conjunction with getting good sleep (especially REM cycles). He says it's absolutely possible to acquire skills much more quickly than you otherwise could, and it directly promotes neuroplasticity.
Acetylcholine, dopamine, and REM are all crucial to learning and integrating new things. Abusing substances may have the opposite intended effect, but responsible use of cholinergic and dopaminergic substances, good diet, and trying to stimulate them naturally can all help.
For example, nicotine patches and choline sources like eggs or supplements like Alpha GPC and Cognizin taken 1 - 2 hours before deliberate skill learning/practice could possibly be very helpful for accelerating learning. For dopamine, coffee is one possible option. If I recall, he said occasional low-dose amphetamine might also help (higher-dose will have the opposite effect).
Anecdotally, I've been possibly following his advice without realizing it. I've also noticed benefits from racetams, which seem to interact with choline systems in some way. (Not sure if the racetams have helped me with retaining knowledge but I wouldn't be surprised, and they definitely do help me with providing a temporary cognitive boost so that I'm more able to digest and understand something complex or play music more fluidly.)
Here's the episode, timestamped. He uses the example of learning foreign languages much more quickly. He's a tenured neuroscience professor at Stanford, so definitely not a crank:
https://youtu.be/ClxRHJPz8aQ?t=6980 
