I personally wouldn't use wet-wipes on the dog, water and a cloth that you can boil wash (if you want to use something that you can wash lots of times) or something like the cheap cloths (those that are like J-cloths) if you want to throw away after use. Wet-wipes (well baby ones anyway) will remove marker pen from almost any surface so are probably not the best thing to use, and will probably sting the dog (try wiping the same area on yourself with one to see if they sting). I don't really know anything about doggy nappies (only human ones) but you'd be wanting something that you could put a liner into it to draw away the wetness but to contain any solids, baby 1 way nappy liners would probably work and are only a couple of pounds for about 100 and you can cut them to size, so they'd last longer. If you are going to use the washable ones then I'd suggest getting a bucket with a lid to keep soiled ones in so that you can wash a few together, remember these nappies should be able to be washed at 60 degrees to eliminate any bacteria that may end up on there.