I would never use 40 grit on anything but thick bondo. Use 80 grit minimum. If you use 40 grit and end up sanding metal, you will have to spray too much primer on there to cover it. You want a good layer of primer, but dont use primer as body filler.

When you sand with the 180 grit, use a DA sander, or electric orbital sander with the sticky pads, and keep the sander as flat as possible to the metal youre sanding(these sanders are expensive, but ask around and see if you might be able to borrow one. If you dont have an air compressor, or if you have one that's too small for a DA, get an electric) If you go up at too much of an angle, your paint job will look like a FLA. (Fat Ladie's A**) The maximum angle you want to have the sander to the metal is 20 degrees, and higher and you get wavy stuff. It's tempting to raise the angle cause you can take a lot of paint off at one time, but trust me from experience, you wont save any time by doing this.

When you get down past your layers and layers of primer and paint, start to use lighter grit sand paper, and go slow. It will be very time consuming, but the best thing you can do for a paint job is take your time. Painting a car is 90% prep.

Oh, and go buy a book on auto painting. there are other ways to paint a car than what I just told you about.

 

Okay whats the guide coat? and what is Wetsanding? I guess I should stop at the sealer Coat because I wont be painting the car myself. This weekend ill do a fender or something. I must do all the prep myself. Im gonna check at my pepboys or advance autoparts to see if i can borrow a sander.
Im not sure which primer to get. Do i need an epoxy primer for bare metal?

 

Oh nvm the sander. I didnt know the sander i had was an orbital sander.

 

Go to a local auto body jobber, and ask for what primer to use. You need a good gun also. Eastwood sells a gun that's good for primer, its around 50 bucks I believe.

And you dont want to stop at sealer if youre not going to paint it yourself. The sealer needs to be put on in the paint booth before painting. Otherwise your body shop is going to be upset if you use the wrong sealer for the paint system.

Guide Coat:
When you spray primer you will get orange peel, to get the orange peel off you wetsand. Wetsanding involves getting a sanding sponge, 600 grit sand paper and a bucket of water and going over the primer in an evenly manner to get rid of the orange peel. The finished result will feel like glass. Now... how do you know when all the orange peel is gone? Two ways, one is by feeling it, and the other is by using a guide coat. A guide coat is a very thin layer of black spraypaint that youve splattered onto the primer. It fills in the orange peel craters, letting you know when the low spots are gone. When you've sanded past the guide coat, youre in good shape. (Just dont sand too much past it, or you'll start to see metal.

To Spray the Guide Coat:
It's really not exact science, but you want to hold the spray can about 10-15 inches away from the surface and quickly with short bursts, put a light spray on the primer.

Here is a car with a guide coat on it.


I'll warn you about "just doing a fender or something." You need to get every single tool and material you need before even beginning to sand. Autobody is a very precise skill, and it take some time you get used to. I would suggest getting all the stuff you need. Sandpaper, primer, spray gun, air compressor, Dual Action sander, and any other materials. We cant stress enough the importance of putting primer on immediately. It depends on your climate, but you could have a rusty fender just by leaving it over night. You would have to start all over again in the morning. So for now just read and do research, then once you feel entirely comfortable with it, dive in.

 

I think ill tackle this after christmas. Im gonna keep my eyes out for a compressor at a garage sale. I really need one. Should i put some primer over spots like this where i have taken rust off.


now it is just bare metal where the rust is.

 

Yeah, sand the rust off with 180 grit and then put some rattle can primer on it. Dont worry about technique, youre just gunna sand the primer off anyway.

 

Could i get away with a 2-3gallon compressor at around 150psi?

 

No way. For painting you need a 20 at least. For DA sanding you need a 50-80 gallon.

 

Ill get like a 20 Gallon compressor, but it looks like ill be using an electric sander. Im poor.

 

Me too, Just wait till you get into college. You work your *** off and you still dont have money.