# Primer build and prep question



## Stratf01 (Jun 22, 2018)

Can you help me understand what situation I want to use a 3:1 build primer or a 4:1?

Also I'm told it's not recommended to wet sand primer on preparation for painting waterborne paint.

Can I simply dry sand with da paper or?
Also what grade of dry paper an I using? 400 or?

Any advice hugely appreciated 
Thanks very much


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## Daveyrach05 (Jul 30, 2018)

Ratios don't really matter, it's more to do with the specific manufacturer.

Primer is porous so wet sanding can trap moisture in and cause issues later down the line. 

Spray a light guide coat and then dry sand, make sure you get all the guide coat off that way you know you've sanded the whole panel. 

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## Daveyrach05 (Jul 30, 2018)

Oh and I use 800grit upwards

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## Stratf01 (Jun 22, 2018)

Thanks very much for the advice!
Does it matter what type of paper you are using?
Guessing wet and dry will clog up quickly or?
Thanks again


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## Danl94 (Mar 10, 2016)

If you're using proper gun sprayed highbuild than you can block sand dry with 320 which is what I do. Finish on 500-800. Blocking with 800 will do naff all sorry to say. Get some decent sanding strips like 3m or mirka.


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