I recruited Lenny partly because he told me that he could heal us. I thought that'd be useful, because, despite having a Doctor skill of 85%, I can only heal about five or six times before I get too tired. I was thinking I would, in the event of serious injury, heal the team as much as I could until I got too tired, then hand the job over to Lenny and let him continue healing us, thereby effectively doubling the amount of healing. Unfortunately, Lenny doesn't seem to understand this idea, and there doesn't seem to be a way of explaining it to him. I can only assume that that's not how his healing abilities work, so how do they work?

tl;dr: How does Lenny heal the team?

The same way you do. All companions will only use their skills like lockpick or doctor if you attempt the action and they are more skilled at the particular task at which point they will do it instead. Its possible that you are a better doctor/first aid guy then Lenny in which case he won't use his skills at all. I'm not even sure the game has any way of treating Lenny's use of his skills as distinct from yours (since you have to use the skill to prompt them) so the cap on the number of attempts you can make with skills that have limited uses per rest probably doesn't change at all even if it theoretically should.

That's a shame. Do followers level up alongside the PC, or can Lenny increase his skill so that it's more than my 85%? If so, then at least I can invest new skill-points elsewhere. (although Doctor is one of my Tag skills....)

Actually, if Lenny is also good at First Aid, I can make use of that. My First Aid skill is only 22%. Come to think of it, since recruiting Lenny, my success rate with First Aid has seemed a bit higher....

Followers do level up and increase their skills but I have never been sure of exactly how. I believe that every time you gain a level all your followers have at least a chance to gain a level but beyond that it's a mystery to me. Wiki might know more.

If the followers are making use of their skills it should be noticeable since they will pop up some floating dialogue (usually something like "let me handle that for you") and then run over and perform the action in place of your character. They don't give any boost to your own skills.

I've not noticed Lenny saying anything when I use First Aid, but then I think I've only used it on myself. Will followers use their skills on the PC?

I don't see why they wouldn't but I haven't used first aid or doctor on the PC with Lenny in the party in a long time.

I'll have to check that next time I'm playing. Anyway, even if I can't get Lenny to cooperate, he still has more HP than anyone else in the team, which makes him a useful bullet sponge (sorry, Lenny), and as I said I can invest skillpoints outside of Doctor once he levels up. Thanks!

This really won't become a problem. You will reach a point in the game when you never have to use doctor or first aid, because you will have an insane amount of stims. My motto always been if I gonna roll with companions then I best take the ones who are good at killing, as combat in FO 1 and 2 is fairly easy and actually pretty quick, as long as you invest in combat skills and aim for them there eyes.

Followers level up for every 3 levels you do starting from whenever you recruit them. They have a Max level of 7, which is really high, for example, Vic gets an energy weapons skill of 195% at level 7.

When you use a skill, if a companion is closer to whatever you use the skill on than your character, and they have a higher skill, they will run over and use their skill instead.