Okay. I have bondo:
Now what?
First you need to do a tribal dance around the pot, if you have a spare virgin to sacrifice to the God of Bondo, it's always good.
Next thing you do is open the pot and look for the hardener, should be in a tube.
Sacrifice another virgin.
Usually you will have to use the pointy end of the cap to pierce the metal seal covering the tube. Hopefully it will have given you a plastic spreader, if not you will need a flat bit of plastic, at a push a small ruler will do.
Dance naked in the rain.
Grab a piece of paper or card, scoop some of the goop in the pot onto the paper or card.
Shout "Ugga bugga wugga Woo!" to appease the God of Bondo, for he is a cruel master!
Squeeze a small amount of hardener next to the goop.
Win a limbo competition.
Mix the two together and quickly but thinly, spread the bondo over the area, you want to try do this as smoothly and quickly as possible.
Turn around, touch the ground, grab your crotch and go "He He!" (What? too early?)
When the bondo starts to thicken up, abandon it and start with a new batch. Make sure you clean your spatula/ruler properly as bits stuck on it will cause indents in the bondo.
Say "bondo bakes better" three times fast.
Go to the sanding stage when done.