Good questions. As it turns out, Most STDs are not spread by hand to genital contact. There are several good reasons for this. In general intact skin is an excellent barrier to infection and contact is not an effective means of transmission. In addition, even if exposed, the skin on body parts such as the hands tends to be thicker, and thus less vulnerable to getting infection than the skin of the genitals which may be more susceptible. Finally, it turns out that the microbes which cause STDs tend to "like" and be adapted to causing infection at genital skin as opposed to the skin on other parts of the body. As a result of this latter fact, it turns out that the types of HPV which cause genital tract infection almost never cause infections on other body parts, despite the fact that there is no doubt than many peole's hands have contacted their partners' HPV-infected skin in the course of sexual activity. There is really no reason for a person to worry about catching HPV through hand-genital contact.
Herpes is a little bit (but just a little bit) of a different story. If a person had open sores/abrasions, etc they can sometimes acquired herpes infections of the hands through hand-genital or hand-oral lesion contact. These lesions are called "herpetic whitlows". They too are rare and there is no reason for you to worry about most hand genital contact- most exposures, even if they are to an infected person do not lead to infection.
STDs, including HPV and HSV ARE NOT spread by hand to hand contact. This does not happen.
Hope this helps. Bottom line, this really is not a major concern and is not something to worry about. EWH
Thanks for the response! For personal reasons (as you likely guessed) I just had to get these questions cleared up.