theres a 2 part primer that uses a catalist and sands easy and not as heavy as bondo...might work good for filliets
How about fine balsa saw dust mixed with just enough easy sanding resin...?
Years ago I was in an "experimental mood" at a time when I had a bunch of douglas fir [lumber] saw dust and a bunch of polyester resin that was going bad. I mixed the 2 together and noticed that....
the wood got darker..about the same shade as your basic, standard grade "dog do"
the overall appearance was that of "dog do" ..[enough to fool anyone]..so it really didn't take much artistic talent to create a few "exact scale replicas" of the real thing.
The family owned gym I belonged to always kept their floors very clean and some areas were carpeted.
They also owned a bull mastiff...[but it was never allowed in the gym].
You should have seen the look on the owners face when she first laid eyes on the very realistic looking "surprise" I steathily placed on her floor .....