Lets see if I can help out with your questions Steve,
I decided to use the TopCote since for two reasons, its worked beautifully on my table saw top to prevent surface rust, and secondly since I needed an uncoated clean metal surface on the doors for the spray adhesive to glue the foam onto. I couldn't use Rust Prevention Magic since you need to heat up the surface which might damage the foam this product sprays on almost dry and won't hurt the foam, you could put a second coat on can't hurt, and you let it sit for a bit then buff it with a cotton rag and that it should protect the metal for a long time. My metal parts had a very light bit of rust and they were 45 years old.
The EvapoRust is amazing in that it only seems to dissolve rust, it appears to be harmless to everything else, won't harm your skin or anything I thru in the pail.
On the clear I have a significant advantage over most in that I have a fully stocked Paint system at my disposal,
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But I'm going to suggest, and this is the product I would use myself if I did this at home, a product call SPRAY MAX, in this case Spray Max 2K Clear Coat Semi Matte (not the straight Matte version). This is a two component clear so it has a hardener capsule inside the can that you pierce by putting the red cap you see in the lid on a pin on the bottom of the can and slamming it down to drive that pin into the hardener activating the clear. You have 24 hours to use the clear then it will be spent and won't spray anymore. These cans spray very nicely almost as good as a minijet spray gun but one should do a few test sprays on something and this will also show you how quickly it dries and it cures up pretty quickly which is perfect for home spraying. Now this is a professional product so most bodyshop supply stores should carry it but you can buy it on Amazon.ca and our U.S. members can definitely get it on their Amazon. It will work perfectly on fibreglass all you need to do is provide the proper sand scratch for it too grab onto like all paints. I used some degreaser first then a red Scotch brite pad since they work great for getting into all the nooks and crannies then I wet sanded the boxes with 800 grit then blow off and degrease before tag ragging the surface (use a nylon lint free tack rag if possible). If you get some of the fibreglass fibres standing up let the clear dry for a few hours then degrease then re-scuff with 800 grit (you won't need to rescuff every corner since the clear will stick to itself without sanding within 24 hours but you should degrease which removes an invisible film that most clears produce while curing) too knock them off then degrease and tack off and re-clear, this procedure should give you the same finish that I achieved.
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Hope that helps Steve, any questions feel free to ask,
Danny