Sanding recommendations?

My Ex tends to have little spots (and some big ones) where rust has made a small hole etc.

I sand these out and use bondo to try to fill in any imperfections even if they are small.

Is Problem is: Can't seem to make the repair unnoticeable - as in you can still see the perimiter of old paint around the repaired area (not in color, but you see a little 'ridge' no matter how small..

Is this just a sand paper grit issue? or should you really sand a "larger" area if it makes sense to help hide the transition (from new to old) paint??

If grit - what grit # do youz go to?

Tips appreciated. This is really a pain.

 

[MONMIX]

Okay, first things first. You must remove the rust. Cut it out, sand it out till you see absolutley ZERO rust.
What I do is remove the paint with 36 grit. Fill it with body filler. ( Other than Bondo, Evercoat Rage Gold is FAR better than Bondo brand )
Shape it with 80 grit. If it feels good, I move up to Evercoat Skim Coat. Hit with 80 till the shine and edeges are gone. Then I jump to 180. One more thin coat of skim to make sure all my scratches are filled. 180 on that.
Remember, the body filler does not like paint. Skim coat should be spread over no less than 180 grit scratches.
I use the skim to fill the feather edges in the paint.
Tips: Make sure when you spread your mud it is going over a clean surface.
Keep your sanding block flat
clean your paper regularly.
Sand in straight lines, but keep changing directions.
Take your time.
Use a old tee shirt between the palm of your hand and the work to help feel your progress.
Don't worry about how it looks as much as how it feels.
Save your final descision till after prime.
Prime will fill some scratches and feather edges.

Best of luck.

 

[Private_Joker]

Great advice. Thank you.
I tried some of the Bondo 'skim coat'. It never even hardened properly (junk I think)

Okay, first things first. You must remove the rust. Cut it out, sand it out till you see absolutley ZERO rust.
What I do is remove the paint with 36 grit. Fill it with body filler. ( Other than Bondo, Evercoat Rage Gold is FAR better than Bondo brand )
Shape it with 80 grit. If it feels good, I move up to Evercoat Skim Coat. Hit with 80 till the shine and edeges are gone. Then I jump to 180. One more thin coat of skim to make sure all my scratches are filled. 180 on that.
Remember, the body filler does not like paint. Skim coat should be spread over no less than 180 grit scratches.
I use the skim to fill the feather edges in the paint.
Tips: Make sure when you spread your mud it is going over a clean surface.
Keep your sanding block flat
clean your paper regularly.
Sand in straight lines, but keep changing directions.
Take your time.
Use a old tee shirt between the palm of your hand and the work to help feel your progress.
Don't worry about how it looks as much as how it feels.
Save your final descision till after prime.
Prime will fill some scratches and feather edges.

Best of luck.

 

[MONMIX]

Evercoat.
Much better.

Did you use hardener ?

 

[Private_Joker]

You need to use hardener with the 'skim coat' (the stuff in a small tube - not for regular bondo work -- filling a hole)??

Evercoat.
Much better.

Did you use hardener ?

 

[MONMIX]

sure do !!!!!!!!!

 

[4.0 freak]

If it is leaving a small ridge where you painted all you need to do is wet sand the area blending it into the old paint and then buff it out.