I've done small decals on my trucks but wouldnt attempt RV side or front decals.
Generally i dewax and dry then use a mild soap and water spray bottle to hit the panel.
once its wet then i generally hit the back of the decal and that allows me to manouver the shape without it sticking,
then start in the center of the decal and swipe the excess water and soap solution out of the application area.
For ones larger than myself.... pay someone! if you dont you will regret having the black fly or june bug in behind it.
2009 Heartland Sundance 31.5 XLT bunkhouse
2013 Ford F150 XTR ECOBOOST
"Of the troops - For the troops "