Welcome to Dustloop, and welcome to the Hakumen side. We excel in bringing the pain >:D Now onto the questions.
1. Its a pretty good idea to understand what his normals are and what they can do. Once you understand them better, it should help you mash less. You can check on this very subforum, or the wiki to help: http://www.dustloop.com/wiki/index.php?title=Hakumen_(BBCP)#Normal_Moves
2. Due to CP's new combo system, combos have be timed pretty quickly. Basically, the timing for the loop gets tighter the longer it goes on(About after the first 5A). The first J.2C has to be delayed pretty late, and from then the combo gets tighter. Just keep practicing to get the timing down, the fortunate thing about Hakumen in this iteration is that his BnB's are pretty simple.
3. I'd consult the matchup threads for questions on characters.
4. Hakumen's oki comes from an Agito ender midscreen, and 3C ender in the corner. Midscreen you can do a typical BnB, but instead of doing J.2A>J.2C>Agito, you do J.B>Agito and you can AD in or back on your opponent depending on what they do and follow up with a J.B. on their wake up. In terms of resets, only thing I really know are throw resets.
5. Beside air grab, the best way to go into OD is off of a confirmed 5C starter.
Hope these helped.