That does work, the issue is that you need to decide right now if you want to train bigs or guards- It is reasonable to train one on one for forwards as you have suggested, as training IS is really good for all players, even for guards it's valuable if you want to play Look Inside or Low Post. But if you want to focus on bigs, you'll want to train rebounding and inside defense as well, which is C/PF (or just C for ID) rather than PF/SF, and you'll want to play bigs in your league games to do that. If you train guards you'll need to train Passing and Pressure (for OD) and you'll need them to play PG or PG/SG for that. Training passing on big men is good for them, but quite slow and requires playing them out of position. So I would decide right now which I'm going to focus on, and then only focus on one group or the other, and selling the trainees from the group you aren't training and buying veterans to fill in for those positions.