Hey dude
I know its tough to hear, but seriously, both Castles and Pumphry are not worth training. The reasons for this is as follows:
a) training is slower for a 21 year old compared to an 18 year old.
b) A $5k salary player who gets a few more pops is still going to only be maybe $6k or $7k salary player, which, is just not worth it.
So really, what im trying to say is the value and reward that you will get from training those guys, is minimal. I know ur attached, and, that does happen, but you will just have to get over it for the benefit of your progression. Maybe keep one as a backup and at best, he can get suppplimentary/secondary training over the next few seasons
With training, you've assumed correctly. one positoin training is always better.With the exception being Rebounding and some other methods, which you can only train at two positions. Id suggest doing some reading up on this in the other forums about training speed, effectiveness, etc just to get you up to speed on this.