This is my first time doing any type of bodywork and for my 69 camaro it would cost $1000 to reweld a fender in so instead I decided to bang everything out with a body hammer and dolly and then use bodyfiller (bondo brand) to smooth it all out... I just keep having trouble getting everything smooth because I have a lot of curves where there is damage.. it seems like the edges tend to be lower than the middle and i keep having to add filler. Maybe I need some sanding 101 tips. How I do it currently is just block sand with 320grit, then 400, then 600 and I can never get it perfect. Can someone give me some pointers.

OK, I'll give this a try. First off you gotta loose that sand paper, your killing yourself, save that stuff for the primer.

Pound the dent out, get it close as possible to original contour. Try to keep the filler to no more than 1/4" thick, I've seen it thicker, but this is the target to meet when banging the metal out.

Rough-up the damaged area with a grinder (24-36 grit). Grind the area several inches beyond the damaged area.

Now, some folks like to apply epoxy primer before putting on the filler, it's an excellent idea, it forms a moisture barrier between the filler and the metal and prevents potential rust from pushing up the body work, but it's not mandatory.

Now apply the filler. Completely cover the grinder marks. Don't concern yourself with completely filling the dent on your first coat of filler, make sure you apply it firmly so there is a good bond with the base metal. Let the first coat tack up, feel/look for low spots, if its obviously low add another coat of filler to bring it up.

If you catch the filler before it fully cures you can rough it into shape with a file. If not you will have to sand it down. For large areas start with 36 grit on a long board or an air file. Now this is where experience pays off cuz you have to know how to read/feel the filler. You'll just have to play with it until you get it right. Here are some pointers.

Initially, just knock down the filler enough to see any low spots, if you see any, stop and fill just those areas. Continue sanding with the 36 grit. You want it to come down uniformly. Work the air file/long board in a criss-cross pattern trying to follow the contour of the body panel. Never sand straight up and down, go at 45 degree angles across the damaged area, switching directions. I sometimes find it easier to slightly tilt the board/air file on it's edge as I start getting close, especially on compound curves.

You should now have all the low spots filled. Now be on the look out for high spots. If you see metal popping through the filler, it's high and you need to lightly tap it down. I recommend for beginners to not use a body hammer to tap them down, instead use a hammer and punch to lightly tap them down (you'll have better control). now you will have to fill these low spots back in, but in order to do so you will have to recoat the entire surface. Don't try and fill just the low spots like I told you initially, You can only get by with that on the very first pass. From here on out, if you need to apply filler it's all or none.

Hopefully I haven't confused you, but now everything should be sanding down uniformly. What your looking for now is the feather edge. If you can see the grinder marks, you should be just about right. Here is where the feel/touch come into play. Run the flat of your hand across the filler trying to feel high/low spots. Take your rings off if your wearing them. For beginners, it really helps to take a slightly damp rag and wrap it one time over your hand and run it across the filler, this will help you better feel the high/low spots. If you find any, then you still have some work. If its high, keep sanding, if it's low skim coat the entire area and sand with 80 grit. Always finish sand the filler with 80 grit.

Now it doesn't have to be dead on perfect, but you want it very close. The primer surfacer will fill minor imperfections in the filler.

Apply 3-4 coats of primer surfacer, mist on a guide coat and block sand by hand. It's very common to repeat this step several times to get it dead on. Now you can use that sand paper you've been using. I hope I didn't get too long winded on ya. Good luck

Rob

Good advice. The only thing I would add is to keep your sandpaper fresh. You need to keep changing it when it gets dull or loaded up with filler or paint. You need the entire surface to be cutting consistently in order for your work to end up straight. Also sharp, fresh sandpaper keeps you from having to push too hard, which can warp the surface while you're sanding and really make it difficult.

In the big scheme of things, if you go through 20 sheets or so, it's not really costing too much.