Hi goon3423,
Just a few tips from a travelling hobo -
For my 4Ground buildings I use dry brushing, all with acrylic paints (mostly Vallejo, but also Crafters).
I clean the MDF kits carefully with "baby wipes" (the cheaper ones seem to work best) to remove the burn residue from the cutting process. Be careful with the thinner MDF sections as they can delaminate if they become too damp.
I find it best to do a quick colour test on the spruces to make sure I'm only toning down and not changing the colours completely.
I've been painting a lot of the Cursed buildings and have only used these four colours for all the weathering - base to highlight -
Vallejo Model Colour 70.821 German Camo Beige
Vallejo Panzer Aces 340 Highlight Afrika Korps
Vallejo Model Colour 70.985 Deck Tan
Vallejo Model Colour 70.993 White Grey
The above colours are also used to dry brush the roofs on my other buildings, too.
To improve the appearance of the buildings, carefully fill any obvious joint positions using some ready mixed wall filler (sparkle) and also paint all the raw MDF edges with a colour to match the buildings base colour. The raw MDF edges can absorb the paint quite a lot so I usually apply a second coat. The window and door surrounds can also be painted in to match their original colour and I sometimes paint the window frames and doors, too.
Rather than hitting the building with an overall dry brush at this stage, I pick out individual boards on the buildings with slightly lighter and darker variations of the base coat. Once the picking out is dry and then carefully dry brush with a highlight based on the main building colour. Again, this can all be tested on offcuts of coloured MDF.
For the walls I work from top to bottom.
Here's a pic of one of the two-storey buildings I'm working on.
As you can see I've tidied up the window surrounds using a dark red/black mix more or less colour matched to the original colour and some of the planking has been picked out in off tones. The dry brushing is slightly heavier on the upper floor, but is applied over both floors. I use rubber bands to hold the building together whilst applying the dry brushing.
Hope this helps.
RMZ