I didn't do any combo buttons, so nothing but wires.
You could do a+b and c+d or w/e on the triggers using diodes, but I had to use my triggers as start/select as the actual start and select buttons on this pad were non-functional (which is why I had it in my scrap pile anyway).
I just use ide wire (which is like 24 awg or something super small) and wired from the pad chip legs to my db15 pins on a female connector. Once I knew all the connectors were good and played with it for 2 days to ensure it worked, I used hot glue to secure all the connections. I like the ben heck method of glue gunning it... i used it like i was injecting money into my bank account.
Dremel up the casing and pcb a bit for a good fit, then screw it all back together. Just be careful screwing the holes for the db15 connector as they are close to the edge of your cut case... so I used a bit small enough to not cause shattering of that edge, but large enough that I would crack it all screwing in the screws.
Again, I'll post pics tonight... but if as for a basic checklist it's just:
- high gauge wire like ide cable (as the pin legs you can solder to are pretty close) together and very tiny
- multimeter
- db15 female connector
- hot glue
- means of cutting the case a bit - (dremel)
- neo extension cable (see Xian XI)
Make sure you don't put too much solder on the legs or you will quickly jump them. So I just carefully tinned all my small wires and then soldered them right to the legs. One thing you can do if this frustrates you, is you can kinda alternate your attachements. The legs are L shaped rather than straight through, so you can do one on the horizontal part that is parallel to the pcb and the next on the vertical going to the top edge of the chip and so on. This made things easier to see and make sure things were staying clean and then check everything with your multimeter if you want to make sure you haven't bridged any pins.
Also, I just left the +5V pin unnattached. Everything else I just wired as you would expect.