I think the photos show the technique better than words! As you can see I like to have a very textured surface. I also leave a couple of bits of the original black foam board to show through, more about this when I begin painting.
The steps at the front of the building were built up with foam board, glued and pinned before being covered with DAS.
For the wall 'plastering' I use DAS that I have added a little water to, it helps with the smoothing out and texturing.
This final photo shows the annex and in particular the thatch. I thought it would be easier to add the thatch to this smaller roof section first and allow me to demonstrate the technique in greater detail. The DAS modelling clay is spread (quite thinly) over a base coat of PVA glue and shaped with a modelling tool to form the thatch shape, the overhang of thatch is modelled on with a sausage of DAS rather than the thatch being that thick! Once I am satisfied with the shape I comb the DAS with the blade end of the modelling tool. The end of the thatch is textured with a blunt cocktail stick - poking the point in to the clay to produce the effect. (At some stage I will take a picture of the tools that I use to help other who wish to copy this technique).
The photo also shows the level of texturing I like to aim for and the black foam board showing through. For sections near the balsa strip I have used the original tool and a much smaller sculpting tool which fits between the beams.
Progress to date has taken about a week of evenings, working about one hour - two hours each evening. Please Note; you have to leave a great deal of time for the PVA glue to set and the DAS to harden.
I try to coat all surfaces that are to accept DAS with slightly watered down PVA glue - I have not had any nasty experiences with the DAS flaking-off, but once read that DAS can shrink if not treated in this way.