I was examining the cowl a few days ago of the TP, after I accidently wacked the fairing in the intake somehow, and noticed that the paint is peeling by the venturi.  The paint has clear urethane over it and I thought it was the most fuel proof paint you could get.

Is urethane even a little fuel proof?

And also, if you let raw fuel sit on the urethane, eventually it will be compromised. I had a plane shot with a pretty nice catalyzed clear and it was upside down in a stand. It had a take leak and the raw fuel ran out and down the plane (the top block, though the plane was upside down at the time). I didn't realize it and it sat there like that for 15 minutes or so. It destroyed the paint on the top block and I had to refinish the top of the fuse. Raw fuel will definitely hurt it if it's left long enough. So say rather fuel resistant that fuel proof.

Matt,
its kind of a catch 22, Its sure easier to spray the clear on a complete airplane, but its really hard to get decent, if any , coverage between things without a gap of 1/4 inch or so, even then, its pretty iffy.
I spray everything in pieces. See pictures Randy has posted about how he holds flaps and such. the motivation to spray it assembled is pretty clear when shooting and masking colors, but you can hold it together with brass strips instead of hinges when you are masking color. Its actually easier than hinges for that purpose. Then yank that bad boy apart when you shoot clear, I even clear it with hatches removed and held onto small paintsticks.

Omni is decent clear, its a bit more Acrylic than 2024 which is what I typically spray.Acrylic makes the clear much more user friendly when spraying and polishing. The 2024 is higher in crosslink concentration, more Urethane,, Its a bit stronger chemically and I beleive higher in UV filters as well.
Nothing wrong with Omni at all.
Might I suggest after the repair, you then coat the inside of the cowl with epoxy, or clear ( since its been exposed to fuel, epoxy may be a better choice) make sure the inside clear/epoxy overlaps the edge of the clear on the outside of hte plane,, to protect the edge. For what its worth, when I spray a plane in parts, most times I can clear inside the cowl at the same time, or I will spray the inside, let it dry, then spray the outside as well.

yea, with cowls and pipe tunnels, I usually epoxy everything and run it over the edges onto the outside. After color is shot and whatnot, I shoot the clear and run it inside the cowl and pipe tunnel to overlap the epoxy. Seems to generally work.

We put finishing resin on the cowls and pipe tunnels and then prime over it.  After that we'll go to paint them when we paint the mainframe.  As I said earlier, there is only urethane on the outside of the cowl, now the inside.  The inside has just the finishing resin.

What finishing resin?

20 minute finish cure epoxy.