I had a cicada and two dragonfly's in a row crammed in my grills. LOL The rain washed the bugs off for me today.
Never seen this wet towel technique. The front with bugs is the only place besides the wheels I use a sponge. Then I use older clay bar on the rest of the bugs. There are so many rock chips on the front that a few minor scratches from the sponge don't matter, if it even makes any.
The whole idea about detailing is less is more IMO. So by soaking caked/baked on bugs you scrub less, saving more paint from being scrubbed hard. Mark