An update on the window sill that I was fixing with Bondo....
I sanded the excess Bondo down with 60 grit sand paper on a random orbit sander. Here's how it looked after I was done:
A few spots left to fill, but overall a pretty good first try! A stiff bristle paint brush is excellent for removing all dust and dirt from the crevices of a repair such as this; important because Bondo needs a clean, dust free surface to adhere to.
This time, I had learned a few things about Bondo. I used an (old) spoon to mix and apply it instead of a putty knife, which allowed greater control. I mixed smaller batches of Bondo, and waited for them to hit "prime" spreading time... about 1 minute in. This is the result:
A little more sanding, and I think we will have it!