Max, it's a difficult one... There are lots of solutions but not all will work equally well.
I've tried the jockless, down-one-side and that didn't work at all! The most difficulty I've had wasn't with saddle sores, but with numbness (lasting about a half-hour after biking) and pressure on the nads (requiring me to bike in a standing position).
When you're given bikes (with poor seats) on vacation there are few options but the 2 that come to mind:
- Always wear clean shorts. The bacteria can promote chafing.
- Lube up. I know it sounds strange, but use enough lube on your cock and balls where it won't create a wet spot. It actually works.
Detailed bicycle seat info
On your bike at home, though, you may want to consider upgrading to one of the many "junk-friendly" seats :) There are traditional saddle-type seats with a gap down the center, which is the kind I've got. Also found this, which is a uniqe variation:
Spongy seat
Hope this helps.