I almost always use PPP for small area filler, but for wider gaps I like the red Bondo filler. Really good consistency, never had it shrink, sands easily enough. I always use masking tape on either side of the gap line, tape very close to the gap edges.
With a small flexible spatula, (like for cooking in really small pans,) I can do a good job of leveling the Bondo so sanding is faster and easier. For PPP a moistened Q-tip will get rid of excess putty in the gap, and around it, very neat job. PPP sands the easiest of all, I think.
To be sure of dryness I let it set overnight, but for small areas like pin holes or scratches, just a few hours is plenty OK. After the tube has been sitting for more than a day, I use 1 or 2 drops of water, literally, applied at the mouth of the tube to ensure the proper consistency.
When finished I add water again to the tube opening, which gives it a much more effective seal against drying. This present tube is 4 years old and the product is still as new.
I think you'll like it.
Patrick