1. Until both male and female have shed after brumation it is a waste of time to put them together.
No.
But it can be more fun to seperate them after a few days and then reinroiduce them and evaluate their behavior for another couple days. Kinda like a green thumb with plants can apply to snakes as well.
2. I should leave male and female kingsnakes together (except feeding time) for several days after both have shed.
Yes I would leave them together and if no activity in a few days I switch the male to another female (if you have a lot of snakes like I do) and this way you don't aster valuable sperm or ovulation time.
Now I have a couple of questions - if both have shed and you put them together but there is no pre-breeding twitching; does that mean that one or the other is either not mature or not ready for breeding? .
I do thing a little less hasty than other breeders so it is a little hard for me to answer this.
I keep my snakes cooled until end of March and then put them together before feeding. They seem to have shed "naturally" with the spring season while cooled and they breed as soon as I warm them up and feed afterwards.If I see the female has not bred then I feed 5 large rodents and wait a couple days before inrtoducing then male again. He is usually busy with another female during this time anyway.
Would you leave them together even if they act like they are not interested in each other?.
I would if I have no other backup male or female. I always have backups so when one is busy the other may be regerating sperm or the female might be developing her folicles. (You can feel the females follicles on her underside) if you feel the follicles she is ready. If not I take the male out for a while to seperate them. But I don't think keeping them together will help. I just stick to the old motto "seperation makes the heart grow fonder" lol!
Also I use paper towel or newspaper in the encloser during breeding to see if a sperm plug is left in the cage overnight (usually means breeding was a success)and then stick it under a microscope to see if they are swimming.
Sorry for the quick response but its 1:30 am here and I won't be around to post again until late tommorow night.