Thanx 
Iād recommend you check out http://punishedprops.com/materials/ and their youtube channel, which has several videos doing almost identical projects. I think they often use a āgreen fillerā for filling/sanding, but they use Bondo as well.
It you use that Bondo again wait until it starts to stiffen up and trim it when itās soft. If it will fit a Stanley Surform tool works great while itās still stiff but not hard. If you keep checking itās easy to tell when itās just right
Many years ago I worked on a homebuilt airplane kit. Bondo was their adhesive of choice for fixtures and holding jigs in place during construction, then completely removed.
Yeah i dont own a respirator yet so i couldnt really check on it after applying it i went inside to keep my neurons intact lol
Use an old fashioned scraper to quickly thin down the bondo. You can get a good scraper with set of different shaped blades at any decent hardware store. A sharp scraper will do more with less dust and noise.