I used Yellow/Grey or standard Milliput epoxy putty to build up the 2p bases. The Milliput was applied with a dental tool and 'cooked' at low temperature for 10 minutes in the oven to speed-up hardening. The cold weather is playing havoc with my modelling time down the shed and the oven cooking was a great help.
Further texturing was done with some sieved stones and sand applied over PVA glue. I then brought the minis into the house so that the PVA would dry or set properly.
I am often asked 'why I base and texture my bases before painting?'
I find it is a much more logical progression as I can prime, basecoat and paint the mini and base in one go which in my opinion gives a much more unified effect and reduces the chance of damaging the miniature when apply basing material after the figure has been painted.