30 - 32 psi HOT is a good starting point. Most competition tyres are measured with tyres at operating temp. If you set pressures on a cold morning and then dont re-check them when they're hot you'll find you're running much too much pressure in the tyres.

Start with same pressure all round. You can change handling characteristics by playing with pressures. If car is understeering, try having 2psi lower in the fronts or 2 psi higher in the rears. General rule of thumb, lower pressure more grip, higher pressure less grip.

Even if it's raining, it's probably still worth having the r-comps until they are really worn.