I like to use a brown primer like Floquil RR tie brown. You can even use Craft Acrylics for this. To get the variation in brick color shoot or brush on what ever red shade you like then take that base color, split in in small containers and darken and lighten the shades then pick out your bricks for color variation. Oils washes wil deepen details and add shadows and bring out texture.
Rubble is painted more or less the same way. Drybrushing lighter tones will break up the objects in the rubble and add texture and demension.
Hope this helps out.