I just wonder why there is no trainer for big guns, unarmed,... in the game. Well boosting small guns is good thing but you have to specialize in small guns to have any profit from boneyard guard's training.
When I start the game as biggunner with only 30% in small guns then 45% can't help me against a simple rat. And also with 45% in weapon skill Gunrunners won't talk to me. So it just seams to me like waste of training.
I think it would be better to tell him which combat skill you want ot boost and he will help you. And also you can chose only 1 and after training he won't talk to you like it is now.