I have seen several posts of members using Copydex instead of PVA.
What is used for removing the Copydex from brushes or other tools?
Maurice C.
Personally I have always bought Copydex in a bottle that has a brush attached to the bottle top and so remains in the glue and does not need cleaning.
However, I have seen posts on various forums that recommend cleaning the brush in very hot water with washing up liquid in it. But it must be done as quickly as possible after using it.
Steve
Heat will soften copydex so warming it in any way will make your life easier. Hot water is probably your best bet although I do not think it will actually dissolve copydex once it has dried. But it may soften it enough for you to work it loose.