You might try a pressure washer and a turbo nozzle. I completely shredded the decals on my Kubota tractor by accident. I was pressure washing it and swung the nozzle over the hood decal. All I saw was this white stuff flying around me. I thought "what the heck was that?" Then I saw what was left of my brand new tractors hood decal. It looked like a wild cat had shredded it. Oh well, I made another pass with the turbo nozzle and no more evidence there was ever a decal there.
If I ever remove my RV decals the turbo nozzle will be the 1st try. I just painted over my graphics last week. My RV looks 10 years newer now. I did clean and prep. the decal by washing, buffing with steel wool, wiping with mineral sprits and rewiping with Naptha . I then painted a vinyl primer to the decal and followed up with a good coat of 1shot sign painters enamel. I chose this because the paint mfg. said their paint could be applied to a vinyl banner if you used the correct primer. I can always touch it up if a bad spot shows up or just blast them off, time will tell. The painting was easy it was the prep that really worked me. 6 hours just to tape off one side. Mike
Mike, Stacy,Preston & Dutch, our German Short Haired Pointer
2001 38.5' Dutch Star DP, 2015 Jeep Wrangler toad