panzer, not sure about the edges, as I have only done this in 72nd and I put an edge around the board. But in 32nd I plan on doing it different. For the expansion joints I cut lines into the base. I have checked out images of relevant aircraft to get the size of each panel, only a rough guess of course. Pnce the lines are cut, I paint in with black artists acrylic. You could use oils as well. Its time consuming but the effects are nice.
Here is a couple of examples, again they are 72nd.
This is my only 32nd one so far. Its on sand, but i plan on doing the tarmac ones similar, and i am guessing this is what you have in mind. As mentioned, i have yet to work out what i will do with the edges, maybe black paint.