When at Ally Pally I watch Sheena Douglas do this technique and she used the new acrylic paints from Julia Andrus which are eco friendly, but for the life of could couldn't remember how, so I have been playing and this is what I have come up with .You don't need much just card wood glue ( haven't tried it with PVA ) Ranger Dabbers and a heat gun. Apply the glue and while still wet brush over the paint
With no water you get more dramatic cracks and the more water you add the finer the cracks .The bottom has regular gold acrylic as a base ( I did try with that but it didn't work ) also the heat gun was put closer so got the blistered effect
Here are some backgrounds I have done some good and some not so good all waiting for just the right images
The top 2 from the left are sandal I used victorian velvet over the top and buffed off the excess humm not much of a contrast the next one was forrest moss good contrast :) next was cranberry over gold .
Bottom left I really like this was a peice all ready coloured and stamps that I didn't like, with the effect on the top and then aged mahogany I love the way that the paints are not fully opaque, the middle was with regular acrylic didn't work, the last one show the effects you can get by aplying the paint in different directions.
So you add a base if you want, the effect and then more colour or start with a bare base and add colour .
Oh and I forgot to say once dry you can buff it to a really nice sheen ... wonder why ?
Hope you will have fun with this