You keep returning to the forum with questions about obviously low-risk or zero-risk sexual events. This is the lowest risk yet -- zero risk, to be exact. STDs are not transmitted through clothing, with or without ejaculation or other genital moisture. Even without clothing, STD transmission is rare by genital apposition without penetration.
In response to a question last October, I referred you to a thread that explains why STDs are rarely if ever transmitted without a bare penis (no condom) inside another person's vagina, rectum, or mouth. I suggest you re-read it.
As an educational point for you and other users, you used "dry sex" to mean genital contact without penetration. However, the terms has another meaning you may not be aware of. In parts of Africa, some women believe men prefer vaginal sex with little or no lubrication, and they insert powders, dry leaves, or other agents into the vagina before intercourse in order to have "dry sex". This may actually increase the risk of transmission of HIV and other STDs. But that's obviously not an issue here.
Regards-- HHH, MD