Dragon, you had me confused on the name of the method at first, but then I remembered the guy who used makeup sponges to do his F-14 repaint nearly 10 years ago
Personally, I’ve not used the sponge-dabbing method on armor or aircraft models, but could see where it might leave a bit of an uneven mess. That might be OK in a way as often the paint on these vehicles was uneven, had sloppy touch-ups, and was generally messy - quite unlike the pristine models we get. The sponge-dabbling method would actually be good for simulating a mud weathering effect.
However, were I in your position, I’d either do a localized repaint using a small paint brush to cover over the numbers or I’d use an airbrush. An airbrush will give you the smoothest surface, but will take some practice if you’ve not used one before. As for paints, several brands make the basic 3-tone German camouflage colors including Olivgrun (olive green) or dunkelgrun (dark green), dunkelgelb (dark yellow base), and rotbraun (red brown). Tamiya, Vallejo, Testoes, Mission Models are all good paints and have either the exact or close-enough shades so you may not have to mix colors.
If you don’t have an airbrush it might be a good tool to invest in. Hobby Lobby stores carry a decent selection of airbrushes from beginner advanced designs as well as compressors. They have a great beginner set that comes with an Iwata Neo airbrush and small electric compressor that retails for about $150 (or $90 with the 40% off coupon).
Hope all this helps
