Believe it or not, but an uncircumcised guy as the top of the sexual relation is statistically 200% more likely to contract an STD through the pocket under the foreskin than that of a circumcised guy.
That's quite a remarkable figure for STD susceptibility - Could you point to the source for it? I think it bears investigating more closely.
As for the foreskin being a germ trap, assuming a fully retractable foreskin, washing takes less time than it generally takes to wash balls. No special thoroughness is needed. Of course if the foreskin is tight, that's it's own problem as mentioned in my previous post and it would be wise to see a decent doctor about it. The reason for not using soap is that there's a little ecosystem of protective bacteria in there which are benign to us, but actively fight off other bacteria. Using soap can knock these out and leave a guy a bit susceptible to some infections.
After having said that, I'm bad at washing with just water and usually clean in the shower with whatever I'm using on the rest of my body. In my 52 years, I've never had any problems whatever with my cock. More than that, I don't think I've ever known anyone I know to have had a problem beyond a standard STD, and with most people I know, we talk openly about such things.