Wet Sand or Body Filler First???

[RTR]

I got my peices primed last week that I had sandblasted (pictures attached). My typical procedure is to wet sand 2 times after priming, then painting with my top coat. I have a few peices this time that will need some body filler to smooth out some dents where I straightened them. Also I have a few small holes to fill where the sandblaster blew through and left some small holes.

My question is.....do I go ahead and wet sand, THEN use the body filler, then sand it smooth
OR
Do I go ahead and fill using body filler THEN wet sand it all at once.


 

[CNKS]

Body filler, epoxy, surfacer, then wet sand, apply more surfacer and wet sand again, repeat surfacer and sand as required. Some say epoxy then body filler, I won't argue about that. ALWAYS use epoxy before the sandable product.
 

[Stephen Newell]

From where you are at, I would do what body filling is needed and where you sand down to the metal epoxy prime those areas again. Once you get the surface where you can't see any more defects scuff sand with 220 paper and use a filler primer and sand between coats until you get the surface level and then wet sand with 400 or finer paper and spray your topcoat. Sometimes when you do body work it will look perfect until you start putting the topcoat on and a couple of defects will show up. If your picky and want to make sure you fix all the defects use two different colors of filler primer alternating the color with each coat. When you block sand stop sanding in places where you are going through to the different color. The sanding will take off the high places and the primer will fill the low places. You will have a much better chance of finding the defects before the topcoat.
 

[RTR]

Is there a special grit/type sandpaper to use to sand down the bondo smooth to the metal?
 

[Stephen Newell]

I use a random orbital sander to sand the majority of the bondo using 80x paper. When I get close I then use a inline sander with 80x paper to get the rest. Harbor freight sells one cheap that works fine. You could also get a hand block that uses the same paper which is even cheaper. Then inspect the body work and see if there is any pin holes or missed spots. You can either fill them with more bondo or use a glaze however unless you are doing a lot of body work spending 20 to 30 bucks for a tube of glaze may not be a good idea. Then I do a final sand with 220 stearated paper with a sanding block and prime.
 

[CNKS]

I start with 80 and finish with 100. As Stephen said you will have pin holes. I forget the typical stuff I use for pin holes, but I have bought it from Wal Mart, it is cheap. You sand it all off until nothing is left except what is in the pinholes. You don't want to use it to fill small depressions, you either use more body filler or you can use a glaze on shallow ones. The sandpaper grit is not that important as you are going to cover everything with surfacer which will fill 80 grit scratches (I prefer 100 grit). I use 400 grit to wet sand the surfacer, PPG says not to use anything finer to wet sand.