You can buy it at wal-mart in the auto section. No need to go to an auto store.

Be careful to NOT get one with "fiber" of any kind in it. Many have short or long strands of fiberglass that are great if you are trying to fill a big hole in a car fender, but are not good if you are trying to fill a divot in wood. The fiber makes it hard to sand smooth and hard to apply in a thin layer.

I would highly recommend you mix up several small batches of the stuff to practice with before you use it. You only have a very short time window after mixing it up to apply it.

But it is great stuff, really good for repairing wood damage around your home. Like outside window sills.

You will get a feel for how much for a ratio.

The mental image I have is a golf ball size blob and ~1" line of hardener. But the 1" of hardener varies by how wide the line is, so once again, experiment.

You don't get much working time with this stuff. Get a good set-up for mixing it fast, but very well. I like steel putty knifes on a a piece of smooth scrap wood. You must be able to scrap up and mix around the material quickly. I have seen people try to use marginal mixing tools and cardboard as a surface, it just does not work well. Either the mix is not homogenous or it takes them too long and they lose valuable working time to apply the stuff.

You can clean up your tools easily if you time it right. The stuff gets firm and not sticky after a few minutes of setting up, but not hard. You can easily scrap your steel tools clean with a razor blade and they are ready to go.

I like to mix several very small batches and build up an area.

What makes bondo great is how fast it sets up and it does not shrink at all. You can put on primer/paint coat ~15-30 minutes after you have applied the bondo. It sets up hard really quickly.

Also bondo has a very narrow window when it is curing where it is like wax in consistency. If you are paying attention you can take a razor and cut the excess off flush with the surface you are filling and it will be a nice smooth surface with no need for sanding. Great for fast filling divots in a cabinet.

The problem is if you wait until the bondo is fully set-up. It will be much harder than the wood in the cabinet and is very hard to sand flush. The wood will sand away quicker compared to the bondo and the bondo will end up being a high spot.