The airplanes I've painted with Rustoleum all have Ultracoat on the wings. I haven't done a silkspan/dope wing since I discovered Ultracote. (I'm going to have to give it a try on the Boxcar Chief I plan to build, it's been thirty years, that should be interesting..)
On my shrink wrap covered wings it's no problem. Rustoleum goes over shrink wrap great, as long as you scuff it with a red Scotchbrite first. Ultracote will iron over Rustoleum & stay stuck too, as long as you give it at least three days to dry first.
As a side note: Don't try to use black on black, the sun does bad things to that combination, even if you use catalyzed car paint, & especially if you have too much Balsarite under it. My black Shark 45 is liable to turn into a Great White Shark if it continues to cause trouble. I should have paid more attention to the wrinkles on my Bi-Slob :/
To repair broken painted wood I first get everything stuck back together as best I can. Then I sand whatever glue is showing. Then I smooth out the nasties with 100-416 Metal Glaze. The 416 sticks much better to SANDED surfaces, glue, wood plastic, anything. The same is true with Rustoleum, sand EVERYTHING. Prime it with PPG waterbase primer (sand the old Rustoleum around the area first with some 220). You can either spray it or brush it on. Let it dry over night, then guide coat it with some black lacquer, sand it with 320, scuff the blend area with a red Scotchbrite, wash it with Windex & shoot it.
All this is fresh on my mind since this is exactly what I'm doing to my Cardinal right now. I peeled the Ultracote off the wings first to get it out of the way. I could have just taken it off the inside bays but I decided it would be faster to recover it than work around it. I was happy to find that even though it was still stuck well to the Rustoleum, 99% of the Ultracote peeled right off as soon as I picked a corner loose. There were a few stubborn pieces on the wing tips but they peeled off too with the help of a #11.
Nils