I have a black gsport birdcage rim. I had a raw flt rim before (the one with holes). My brake is perfectly adjusted. So far I have tried:
Clear Odyssey slim by four pads
Black Aztek pads
Natural (red) kool stop pads
Clear Fly pads
My brakes slip way too much. Guys from Odyssey said that all I needed was to clean my rim with soapy water. Ive tried that and it didnt work. I also tried with coke and same got the same results. They squeak and work for no more than 30 mins. After that they slip. I hate that. Got any tips?
I noticed you didn't mention the brake cable?
I've worked on dozens of bikes and brake setups, and although various things work slightly better or worse, the most consistent thing that seems to make the most difference is having a smooth-pulling brake cable with no kinks, minimize tight bends, and FULL of lube.
If you're talking about a front brake cable, then if you've used it on one bike then remove it and put it on another bike (or back on the same bike), it often works less well, because you've already kinked it where it comes out of the fork above the tire.
People often also have a kink in the inner cable close to the brake lever, as well as near the rear cable stop that goes to the splitter; those kinks will weaken the pulling power as well.