Sandable filler as soft as drywall mud?

[helix_3]

I'm working on large-scale sculptures and I need something soft and sandable to go over a coarse armature. After this I will apply a solvent-based 2k/ 1k/ paint/ etc over the top.

I have considered these products:

• Expanding foam- Cheap, quick, and easily formed, but would be dissolved by solvent-based products
• Drywall mud- Cheap and extremely sandable, but water-based and therefore slow drying + poor compatibility with solvent-based products
• Bondo- Affordable, fast curing, and non-water based formulation. Best option so far, but it is too hard to sand for my tastes. I can roughly shape it with power sanders, but I'd prefer something softer that can be more carefully formed using hand sanding

Is there a product on the market that sands as soft as drywall mud, but is non-water based and quick curing like Bondo?

 

[TazMan2000]

I'm working on large-scale sculptures and I need something soft and sandable to go over a coarse armature. After this I will apply a solvent-based 2k/ 1k/ paint/ etc over the top.

I have considered these products:

• Expanding foam- Cheap, quick, and easily formed, but would be dissolved by solvent-based products
• Drywall mud- Cheap and extremely sandable, but water-based and therefore slow drying + poor compatibility with solvent-based products
• Bondo- Affordable, fast curing, and non-water based formulation. Best option so far, but it is too hard to sand for my tastes. I can roughly shape it with power sanders, but I'd prefer something softer that can be more carefully formed using hand sanding

Is there a product on the market that sands as soft as drywall mud, but is non-water based and quick curing like Bondo?

How about Plaster?

TazMan2000

 

[Duncanator]

Maybe you could add a filler to the bondo like micro balloons, fumed silica or fillite ( Fillite, 1 lb. ).
These extenders should soften the finished product by adding porosity. This would also likely lengthen the cure time, but that could be offset by increasing the catalyst.

Expanding urethane foam should be a good choice too. It won't be dissolved by solvents like styrofoam will.

 

[PHArchivist]

Elmer's Wood Filler

 

[helix_3]

That's huge knowing that urethane foam isn't bothered by solvents, thanks!