I got the #20 SG to take a RS without informing him during recruiting.
I believe I've tried nearly everything the book, not putting a player on the depth chart, waiting until after exhibition, waiting until after non-conference before trying. So on and so forth and haven't noticed a higher or lower success rate of the player accepting the RS. I believe it's just dumb luck whether they take it or not, but someone else may have found the correct code.