Replies

1. 
   SteveSchoene | Jul 25, 2010 06:01pm | #1

   It depends on the brand, but for some traditional fillers such as Plastic Wood, try acetone. 

2. 
   bigfootnampa | Jul 25, 2010 07:03pm | #2

   Steve is right and you can also try lacquer thinner

   Many woodfillers are just wood flour or similar filler mixed with lacquer.  This is especially true of the ones that tend to harden in the can.

3. 
   ubc | Jul 29, 2010 09:43am | #3

   If it's a letax based filler like DAP's add a bit of water and mix well.

   It helps to keep the lid and rim of the can clean allowing a good seal.