Normally when people do this they say they reduce the clear around 25% also, I hear this quit often but keep in mind I'm not a custom painter, so others can advise you better.
I have with Universal when used as a carrier reduced it 50% one time to add peal to a new black vette and reduced a 100% to add peals to a new black Nissan truck.
Seemed to work good.
Like Bob said sand next day or no sooner then 4-6 hours.