Plazmatic CRM pads and Koxx pads are both suppose to be very good, you grind your rim a) for more power, and (Y) it helps braking in the wet , you can get tar from building suppliers, or if theres a building site nearby which mite be using tar, just ask for some and im sure they mite give you a small bit (You wont need much) When you have tar, then you can just make little lines going round your rim, or any other pattern. You can put a heavy grind on your rims or just a light grind, eventually the grind weres away.
Hope i helped
Jules