Well when i still had a trainer, I always trained em for two positions, and stayed with that for three to five weeks, before changing it up. I would try to train the whole team too, not just a few players. Although that didn't always happen.
My starting 5 besides my C can play all positions. Khan is half way there, but his progress has slowed down, obviously without a trainer.
To answer your other question, we would sell em if we were deep in that position (3 max per position) just incase of an injury.
This season for us, its just throwing backups in, and hoping they have a good game, because there's no training going on, besides, stigma, and free throw shooting, so there's no chance for them to improve.
Romeu hasn't been the same player for us, only scoring 13 total points in two games i think. And he's takens less shots, in a season we need him to shoot more.
Its been a tough start to the season, were lucky to be 1-1. It's early tho, no need to panic yet. We got off to a slow start last season too. Were not a good, early season team, but we seem to turn things around late in the season, for whatever reason