A pressurised stream of water, aimed directly at the unclean hole in question, will usually do a good job of removing most of the unwanted matter.
Technique is something that will need refining and we would recommend “swings and roundabouts technique” in a forward and backwards and around and around motion.
However there is still the schrodinger's cat (or schrodingle berries) question of it could still be a bit dirty or clean but you won't know until you have checked.
This opens up the cheeks of different schools of bum gun perspective.
In a lot of cultures they would spray to reduce most of the mess then they would use a specific hand to ensure it was clean as one would do in the shower, then wash their hands with soap.
This is supposedly where the term cack handed comes from, where in certain cultures they would have a specified “dirty” hand, usually the left, because they wouldn’t wash with soap after using it as a wiping device, and then have a specified “clean” hand, for eating and so on. Adopting this technique does ensure your rear end is clean, I would recommend just thinking about keeping one hand clean for holding the bum gun, flushing the toilet and turning on the tap.
I would also like to point out that dry toilet paper will very rarely remove all of the faecal matter in question, and if you try, this usually results in scratching off a few layers of skin down there!
Therefore one will only become clean when they have washed their rear end in the shower where they will very likely come into contact with their own faecal matter. So this is not a new experience.
Therefore if you don’t want to get your hand dirty, and you have given your rear end a good old hose down then drying with the bum towels is fine, and if a bit of faecal matter does end up on a bum towel, think of it as a skid mark, a sign to refine your technique, and wash it as you would a dirty pair of pants!