I feel the same way about not wanting to get any of load on my clothes either. In addition, I don't like leaving behind a mess, it's disgusting. Even though I'm a hairy, horny guy that has all he can do to keep his dick in his pants, what I do shouldn't affect anyone else. ANYWAY, I like to get my pants and underwear down for a feeling of complete freedom when I'm doing it. When I'm on the verge of cumming, I make sure a.) I'm leaning forward far enough, and b,) I have a paper towel to shoot it into and wipe my penis the second I'm done ejaculating. (Have a small trash bag to put it into.) After that I pull my briefs up, then my pants, and I'm done. Hope this helps. If I sound like an expert, it's because I am. I've done it many times, and will be doing it many more---for sure.
I have done this a few times when there are a few people on the bus. I rarely shoot my load because i dont want to make a mess on my clothes. So fucking exciting!