Dont do it in the sun! brush supplied is usually crap, get a good quality "fine piont" brush and some thinner for brush cleaning from a artists supply/model shop
Try and fill the scratch with paint, wihout it spilling over onto undamaged paint, build up in layers one stoke at a time, let the paint dry for a few minutes between strokes..
Apply clear in one stroke, dont keep going back to it trying to "make it better" unless the previous coat is dry!
Make sure car is washed, with no wax residue left in the scratches or chips
hope this helps
Tom