Never have, usually clean with some sort of degreaser real quick, quick dry with compressed air and spray away. Have a couple rifles that get used/carried every few days, paint stays on plenty good.
I use lacquer thinner to clean and degrease, and put on several thin coats of HS Camo permanent, or Krylon camo-and then sometimes cover with flat (not matte) clear for an extra layer of protection. It holds up really well.