When I was in the Oxford Street Games Workshop the other day I picked up some Liquid Greenstuff. This sounds to good to be true. A medium you can paint on with a brush and it dries hard and can be sanded and scraped... Well, it is true! It's quite a gloopy mixture, really thick, but using an old brush you can apply it really easily. The impressive thing is the speed in which you can apply it and it dries. Only takes a few minutes.
It's perfect for small holes and small gaps, anything bigger will require regular greenstuff. Cleaning your brush is as simple as using normal paint, just wash with water and wipe with a clean tissue. I will be using this a lot on the Thunderhawk because it's just so fast and easy to work with.
I wouldn't leave your pot open for too long, I have a feeling it would dry out pretty quick. I'm not prepared to test that though.