Be patient...im paintin some valve covers and doin a REAL crappy job because I get bored and impatient. Clean em as best as you can, then rub em down with some alcohol or paint thinner to get any grease or finger prints off. Primer is a very smart step and then hit it with some engine paint. That paint is very forgiving and easy to use.
Matt
are the heads new or have they been hot tanked? if they're greasy you'll want to hit them with a good grease and wax remover or even a wire brush at first to get them as clean as possible, then hit them with some engine paint... my personal preference is the duplicolor hi-heat engine primer for about three coats, then engine paint for another two or three coats