Training your players is quite easy in a bot league too, as you can submit 5 player lineups which will almost guarantee you get perfect minutes (sometimes a player gets fouled out or injured though).that's why you have to register few more players for the game, but do not use them in any sub place, so they`ll be used just in cases of someone fouled out or injury, so you wont loose those minutes.
Training your players is quite easy in a bot league too, as you can submit 5 player lineups which will almost guarantee you get perfect minutes (sometimes a player gets fouled out or injured though).
I wouldnt do that, as it messes up your minutes if you have a blowout win as the computerized coach makes wild substitutions in that case.
But be careful: Playing the whole match will drop your players stamina faster. (no matter how many minutes they got on pitch in the week)