Had a tube of Squadron putty dry out on me, I heard it thins with acetone so I put the rest of the tube in a large Tamiya bottle with some nail polish remover. Being thinned down, its a LOT better than out of the tube. Smooth, easy to apply thin coats with out lots of waste. It sticks to the lid a little which happens to be great for getting it to your tools.
You need to check it every week or else it'll start to dry out and need to be mixed.
If you're gona use Squadron, its what I suggest. Right out of the tube the stuff kinda sucks