These are the steps I take when decalling:
1.make sure the surface is glossy, use future or a clear gloss. Allow it to dry for a few days.
2. Apply the decals. Put some micro-set (or similar) on the surface first. Then position the decal and brush a little more MS on top. Wait about 5 minutes and press down gently to remove any air bubbles. Then brush on some micro-sol. Just brush on a thin coat and let it do its thing. If there are any bubbles in the decal after it has set, prick a hole in the bubble and apply some more micro-sol.
3. Once decals are dry, apply another clear gloss coat over decals. This helps to hide the carrier film of the decal. Once dry, you can do any weathering you want.
4. apply several coats of your chosen flat clear. It's better to apply several thin coats than one thick one. A light sanding between coats can also help to conceal decal carrier film.
That's it. The best way to get good looking decals is to use aftermarket ones. They are usually alot higher quality than the ones you get with the kits.
Hope this helps.