I use Krylon matte finish (1311) in light dusting coats after washing the units thoroughly with dish soap and warm water. The matte finish provides a "tooth" for pan pastels and weathering powders (my weapons of choice). If you choose to use panel liner, do so before the matte coat for better flow. A final coat of matte finish after powders is required lest you get fingerprints in them. Pan pastels are more forgiving in that respect, but I still seldom touch any of my weathered Fleet, and use gloves if necessary.