I am having problems when applying clear coat to a 2 stage polyurethane, the base coat goes on o.k, but as soon as i put on the clear coat it starts to get small craters in the paint,i used to paint 20 years ago & havent used this 2 stage products, in the old days we used to call this similar defect called fisheye, ( talked to a partner who thinks i need to use wax & grease remover before putting on the base coat) can someone please help.