But you cant (shouldn't) really do that.
Shotgun skills are not going to work on bows and vice versa. When it comes down to it, without a complete respec, you sort of have to pigeon hole yourself into one type of weapon (ie: going with a shotgun early on, then pumping skill points into shotgun specific skills. Or going dual pistol and pumping skills into dual wielding etc). you can't successfully flip flop between weapon styles.
I started a new engineer, and had a hard time deciding between two handed sword and shield and sword. I put 3 points in sword & shield skills, and now regret those 3 poitns as I have been nothing but 2 handed swords, and am now level 36. I WANT THOSE TWO POINTS BACK!!!