Unless there is a medical reason, dogs do not need help cleaning their parts.
Dogs should only be bathed a few times per year, it strips the coat of its natural protective oils and perfumed soaps can be an irritant, especially around genitalia.
Some dogs may need help keeping the area trimmed or shaved, some dogs have bad aim or their fur is too long or fluffy so a sanitary trim done by a groomer can be helpful but overall males are fine on their own.
If you are concerned you can take a baby wipe and wipe down the sheath and dab ever so lightly at the opening before any activities, otherwise leave it alone. Male dogs are not into anal play so leave that area alone.