Hi,
If you wanna go that route, bronze spring arms are better than carbon.
A thing to note: You need to have extra capacitors after the slip ring, since it will bounce off for short intervals (µs to ms) every now and then and a µController will tilt, if it sees that kind of interruptions.
At 100mA draw, 2'000 µF will buy you 5ms before the voltage has dropped 0.25V and that should be enough - unless the slip ring is very poorly made.