I’m not normally one for blood splatter or mud (Angel’s demon had a dry brush around the base of his cloak and that’s about it), but the bulk and weight of the daVinci tank did call for it...
I wasn’t going to buy anything just for this, so just stippled on Vallejo earth texture and gave it a dark wash. Probably better ways to do it, but worked and serves to hide the sins of wonky handmade wheels...
