depends on what kind of paint- oil paint? latex paint? water based paint?
linseed oil mixed with oil paint can revive it unless it is too far gone.
paint thinner will work with most other paints- but it depends on the kind of paint.
My Dad heats it up outside, but you have to be careful not to get it too hot, or it could start a fire. He uses a small torch and gets the paint nice & warm. I'm not sure if it only works on ceratin types.
Acrylic is a water based paint so you could try mixing in some water and see if it helps.
There is a thing called white spirit you can use. Other then that i don't think so.
I would say NO. You are better off to buy new paint.