What is in 'stealth paint' to reflect radar, and how does it work?
Stealth paint doesn't reflect radar, it absorbs it by converting it to heat which is absorbed and dissipated by the airplane's structure. Paint is only one of several Radar Absorbing Materials available. 

The paints known have suspended balls of ferrous material which absorb radar energy at certain frequencies and convert the radio energy into mechanical vibration, which causes friction and in turn heat.