Spraying

Does anyone know the best way to prepare the surface on the car, namely the GTA doors, as mine are now blistered. Can i just spray them with an undercoat once they have been sanded down? Or will these blisters reappear.
Any suggestions will be welcome for me and my sprayer.
Dave Miles.

You need something like a Dremmel to grind out the blisters. Run it along them (down the lines of the blister) using a 3-4 mm bit. Then get hold of some Gel-Coat (you'll only need a little) from your local fibreglass laminators.
After that has cured, rub the area to be painted down firstly with 150 grit sand paper and then work the grade down to 600 grit.
Nearly done - just give it a wipe over with some thiners and then a tack rag - ready for paint.

Make sure you get all the blisters out and filled, if not, they will always come back through.

The blistering was a fault in the manufacture, where resin that never set completely and absorbed moisture expands in winter, pushing out through the plastic and bubbling the paint. Its very hard to get rid off. You need to sand right back to bare plastic, scrape away any excess residue, or resin (really bad parts need cutting out and re-filling, and then block off with a good filler all the pinholes where the bubbles would have come through. Basically, sanding the plastic opens it up to breathe (its also been advised to bake the panel in a sprayers oven before painting). You need to block off the panel to seal it up again.

Be prepared though, as it still may come back.....