No war with me, but I'd suggest setting the "lump of bondo" on plastic and then arranging the feathers into the bondo. That was the reason for not mixing it hot, so there would be more working time.
If I was worried that I couldn't work fast enough, then I may hot glue into place with one line of hot glue and follow up with the bondo.
There is no right or wrong way, just a preference.