HELP with bodywork

rednesss said
Actually the water cleans out the "dust" from the areas between the aluminum oxide that comprises what makes sand paper, sand paper, and doesn't allow the paper to be clogged with material, soft talc, that will make it so that the grit doesn't contact the surface, but just push around the sanding dust. After about 2 seconds of sanding look at the paper, you'll see it is full of material, talc, etc.... now rub your hand over it and compare to a clean sheet. Wet sanding always keeps the grit "open" and thus more abrasive.

I agree entirely, wet rubbing definately gives more cut than dry rubbing as rednesss has mentioned above, not only that, if you wet rub with a garden hose on low pressure it actually helps to remove any tiny grit particles from the paper and reduces the risk of sand marks/scratches caused from dirt or grit caught in the paper. I'm not a tradesman but I would class myself as a semi-pro as I've painted at least a dozen cars and wet rubbing primer (not bondo) is fine. Once I've hi-filled and all my repairs have been done I always prime it and guidecoat it then start wet with a 400 wet rub. Then prime it and guidecoat it again and give it a final wet rub with 600 or 800. Just make sure that you give the suface enough time to dry after wet rubbing before you apply the next coat of primer. If you're intent on using aerosol cans (bombs) I'd advise going as fine as 600 on your first wet rub as the bombs will not give the desired coverage of a spraygun and you won't lose as much of the product (primer) when rubbing. Of course the bomb approach is not ideal, however if you have no other choice then I think for primer it's ok. I hope this helps.