When I was soldering those points I aimed for the largest area of the contact point.
Scraped the carbon off and touched it with a dab of flux so the solder and tinned wire would stick better.
Ok. I’ve scraped the vias for the directions but no matter what I do I can’t get the solder to go on to it, it all ends up on the iron with none on the via.
I touched the iron to the via for 4 secs so it can heat up but the iron still takes all of the solder.
I’m using a cheapo Rat Shack iron. Maybe I need a different kind of tip?
are you using rosin soldering flux? i’ve found it really helps the solder stick.
Just rosin core solder (supposed to have flux inside).
I too found the tiny copper pad impossible to solder to. Use the vias! SO SO SO much easier. Piece of cake.
Follow the traces back to the vias/through holes. Open them up gently with a scalpel. You should be able to push a thin strand of wire through the via and have it sit in there while you solder.
Place your iron in the via next to the wire on the surface of your PCB. Let it heat a few seconds. You only need to add a little drop of solder. You won’t be able to get nice blob of solder covering the whole thing, BUT some solder will go into the via and secure the wire. To check, let it cool half a minute and gently tug the wire. You’ll feel that it’s well and truly bonded. Secure the wire with a blob of hot glue. Diagram is here and here
The via for DOWN is easier accessed from the underside of the PCB (unless you’re removing the analogue sticks).
I read that you shouldn’t hollow out prefilled via’s as it can ruin the trace (from connecting the top to bottom of the pcb).
Also, is your yellow wire secure? It really doesn’t look it 
I also found out that TP9 on the back of the pcb can be used for Dpad Right unfortunately its right under where the battery pack would go so it might get disturbed (I’ll just have to use minimal solder).
you should get some rosin soldering flux. i have the paste from radioshack. it makes a huge difference. i just dip the tip of the wire in the paste and then paint the paste onto the spot i’m soldering to. you just need the tiniest amount and it makes a world of difference.
Hollowing the vias may ruin the trace, but I’m no longer using the trace beyond where my wire goes. As long as the button I’ve wired up works and is secure I’m happy.
I’ve hacked two MS360 wireless late version pads using this method and they both worked first time, no problems since.
The yellow wire might look a mess, over-did the solder, but it’s very secure. Far more than I’d expected. It’s a thin strand of wire though, so to prevent that moving, and getting brittle to the point of snapping the wire is hot glued to the PCB further down it’s length.
Also, this method works for the SYNC button too.
Soldering to this other point you mention (by the battery pack) sounds interesting. Good to know there is another back up.
Ok, ive got a SFAC stick that i re-wired completely. I then started soldering the points on the wireless common point 360 pad and i had it all working fine. I did the face buttons, guide, start, back, etc, everything worked perfectly. When i got to the D-Pad, everything took a turn for the worse. I could not get a good connection at all and then all the material for the d-pads burned off. I tried to solder the alternate points in the back with no luck, nothing sticks, but im afraid to scrape off too much from the top. How much do i take out? Or do i just enlarge the hole itself and then stick a wire inside? Im using 24 gauge and its pretty thick. I need some further assistance because all i need is the up, left and down and im done with this sucker. Ive already wired up the bumpers and triggers and the trigger ground. Just need those 3 d-pad points and im done (the right d-pad has a large pad on the backside thats easy as pie to use).
This is the first time ive ever done anything with a arcade stick or pad hacking btw, so please be as clear as possible.