After Jen posting her thread showing her new base, I caved in & had a shufty at these lovely looking bases from French company Mark.58, available in the UK from Modelsforsale.com. They look impressive on the site, but when my chosen one arrived (28cm concrete), I was amazed at both the detail and the color, which VERY closely resembles real concrete IMHO.
Lifting out of its cardboard box & foam liner (good to keep for transporting), I was surprised by the weight & sturdy feel of the base, which feels more like porcelain than resin. It also has a strengthening mat moulded into the base, which would probably come in handy if you ever dropped it
Anyway - I thought about laying on a primer coat, but couldn't bring myself to do it, as the color of the base was so good already. Instead, I applied different mixtures of Tamiya Flat Earth and Flat Brown to the joints and crack lines, which looks quite effective to my untrained eye. There is a section of groundwork to one edge, which has a texture that could be painted up to look like either grass or gravel/mud. I painted mine with an undercoat of the aforementioned Tamiya browns, and then laid some various greens over it, highlighting with lighter & lighter shades. Looks ok to me, but your style may differ.
I added a couple of oil stains using a weak mix of oil paint & white spirit, dabbed on & allowed to spread as it saw fit. I used a couple of different colors & stregths to give a bit of variety, and added a little extra variation to the concrete color of the slabs with some CMK pigments.
Total work about 90 minutes (mainly painting the joints), and to me it looks great, and required little skill on my part! All that's left to do now is to paint the edge of the base to hide my goof with the green paint
And again with one of last year's completed models, the Dynavector Scimitar
Well worth the asking price, and I'll be getting some more as funds allow
Sample courtesy of Modelsforsale.com and my pocket.