I've been thinking of short hop charge partion in order to get in and make sure you have an Gatlin' prepared. It's hard to do, but I don't think it's possible to do it after a dash in.
Also, I think Clark's st.B could be used as a frame trap. If it hits you can combo into whatever, including A Gatling. If they block you can do s.C (and technically it combos if you're fast enough) and that will hit them if they try to jump out. Or pretty much anything else on block, like dash in D SAB, st.B then B SAB, or Sweep, or throw in s.D as a poke.
I'm starting to get better at his standard HD Combo
I'm averaging around 550-625 damage though. For some reason I can do it really easily if I do cr.B, cr.A, HD, A Gatlin' and etc. But if I do st.D, HD, and A Gatlin' it feels kinda' random. Most of the time I just get st.A. The timing is weird.