I actually started doing pullups during one of my cutting phases, just to try and maintain a little strength. 20min stepper, 2 sets pullups, 20 min cycle, 2 sets pullups, 20min skipping, 2 sets pullups.
As it turns out, when I went back to bench press after 2 months, my 12 rep max had improved by about 10kg. After another 2 months I was up another 10. Pullups are the BEST thing I have ever included in my workout. I never bothered with the underhand to be honest, but now they are a piece of cake.
During this cutting phase:
-When I started, I could do maybe 2 normal grip pullups with correct form.
-Started with a narrow grip doing 2 sets of 6 or so (with assistance either from a buddy/ one foot on a bench to remove weight)
-Moved on to normal grip after a week or so. By this stage I could push to about 8 with a spot. Did the normal grips for a good few weeks, trying wide grips every now and then but the motion makes it super difficult, so I just stuck to normal.
-Wide grips are MUCH harder, but force yourself to do them. I dropped back to about 6 reps, but gradually worked my way up to 12. Now I can't believe I struggled to do 2. And I don't know if everyone has these Technogym machines, but my lat pulldowns improved from 6 reps of 60 to 6 reps of 80
If I had to make a list of tips:
-F*(K what everyone thinks when you can only do 2 reps. The occasional stares you get when you can do an easy 12 make up for it later.
-Don't cheat. Let your legs hang and avoid using their momentum to help you.
-Your spot should push up between your shoulder blades, not offer you something to push off by supporting your legs.
-Do not do pullups 2 days in a row. Allow your body to recover for at least a day.
-Don't use that counterweight machine thingy unless you are just starting out. It just doesn't feel right. Go straight for the proper pullup bar if you can.
That is what worked for me. Got me past a serious plateau on chest and back.