I've been attempting to work on my grips, in addition to strength. Primarily, I've been working on closed-hand (or full-crimp) and pinches.
Unfortunately, my hangboard doesn't provide a great place for either one. It does have some pretty small lips, which most people would hang on with a closed-hand grip, but I'm having trouble. Closed-hand grip tends to have your knuckles standing up, and my hangboard has multiple tiers, which get in the way of my knuckles. Also, I just don't plain understand the closed-grip.
Here's an example of the closed-grip (via LoganG)
The closed-grip tends to put more strain on your joints and tendons instead of on your muscles and skin (friction). When I try to do the closed-grip, I feel weaker than with an open-grip. I think part of it is that my arm is forced into a slightly different position, due to having to curl my wrist to place my thumb on top of my fingers. There's also significant risk to joint and tendon strain when placing a lot of weight on them in this way. This is actually a quite common cause of injury to climbers, especially newer climbers, like myself.
Here are the two grips on my hangboard (from Blankslate)
When doing a session on the hangboard (which I try to limit to around 15-20 minutes, to prevent strain) I try to do at least 3-4 sessions of 5-10 second hangs with each grip I'm working on. If applicable (not really for crimps - maybe a couple), I also do pull ups with the grip, which is more about maintaining the grip through a pull than strengthening my arm.