|This will be a fast food takeaway with entrance and exit doors.|
I've smoothed over the interlocking cut corners with filler. Rather than use water, I've used paints to mix up the filler, this seems to give a better texture for application and sands to a good finish. I've used Wilko emulsion tester pots which I've found to give excellent coverage. Each building received a couple of coats of white MDF sealant, then a very gentle sand with a fine grade foam sanding block. After wiping off the sanding dust (I just use a big, soft brush) I've followed this with a couple of coats of my chosen colour, again sanding between coats. This gives a nice smooth finish and helps conceal any grainy or fibrous texture from the MDF.
There are a number of other web sites out there with nice examples of painted buildings from MMG, my two favourite so far are Marja's Miniature Adventures and Dropship Horizon.
Here are a few of the storage containers I got in the same order. These are fantastic value, just what I need for filling up table space with large objects to provide cover. I've assembled some with the doors open, these can act as objectives for certain scenarios.