If I start on a freshly painted wall I do no prep, but if the wall paint isn't pretty fresh, then I'll wash the wall with warm water and maybe a drop or two of liquid dishwashing soap like "Dawn" to help remove any grease or oils. From that point I'm ready to paint. When I'm done I normally don't need to clear the mural, but in the case of the restaurant murals we did clear those by rolling on a clear polyurethane....But as noted by someone else, rolling on a clearcoat over your artwork can cause problems by lifting your artwork...fine oversprays are the first to lift, but heavily appled areas don't seem affected as much, but if I have to clear anymore murals, I'll probably spray those using a full size paint gun or an airless gun.....I've also applied Future acrylic floor finish as a final clear coat with great success, but I applied it with a large sponge brush over mostly automotive paints and didn't have any lifting issues whatsoever. But over waterbased acrylics I'd still be carefull with it. Most of the following murals were painted with waterbased acrylics, but sometimes I used SG100 mixed with kandy kolors to get the color I wanted, as in the case of the monotone color murals....thats sg100 intercoat clear mixed with red iron oxide toner from PPG.
The bike mural is painted on a cinderblock wall, and was a major pain in the you know what.....The mexican restaurant murals and the Ratfink style and 4 wheeler mural were painted on relatively smooth drywall....the Branding Iron mural was painted on a heavily textured drywall surface that caused all kinds of overspray issues simular to what I fought when dealing with the cinderblock wall, but all in all they turned out looking ok.
I start on a mural for the local RC flying club in the next week or so....I'll post some pics once I get going.
