Yes, I realize you're probably getting sick of news about blast holes and sand and whatnot... but I'm working on finishing this stupid table, so sit still and take it (and besides, there will be cool stuff later).
Made a bunch of scrapes and holes in the otherwise perfectly nice foam table I did.
I filled the hole first with watered-down glue (about 1:3 glue:water). I didn't even "paint" it on; I just poured it in (with masking tape around the edges so it didn't roll out). Then I poured coarse sand on top. Later, I put more watered-down glue and added some finer sand (also around the hole) as well as some plasticard "tiles" that would look like they were blown off the ground (this effect was helped along when I burned the edges of the plasticard tiles with matches).
Sealed it with more watered-down glue (it's better to put on too much than too little), painted it all black, drybrushed Shadow Grey (color-matched by Canadian Tire), Bleached Bone (about half a pot of GW product) and a dusting of Skull White (which is great for drybrushing).
This part of the table is done. Once I do the other one, the whole thing will be done and I can move on to finishing up the scenery and Cityfight stuff.