>Use them.
>Let them get some major kills
>also, don't do everything yourself.
>
>I CANNOT prove this, but it seems to work.
>But remember if you let them get most of the kills,
>they go up but you don't.
I'm not sure if your statement is accurate.
Basically the rank system for the recruits isn't a major factor in the game, except for your main character. So far, my character has gained a rank after every mission, which effects who you can recruit. Charisma should also affect recruitment but it really doesn't in the game. Bug? probably..
After patching the game to v1.25 I've seen 3 out of 5 of my team mates gain 1 rank where my main character has gained 5 ranks. And to top that all off the characters who gained the rank don't do the killing, scouting, lockpicking or healing. So I think that the rank system is still flakey and should be affected by the Charisma of the team mate in question along with their activity in the team. If they are important and heroic, they should be rewarded by rank stature.