Surprise ass play is never the move, so check in before trying that explicitly—but plenty other areas are available. If you feel a little more confident, try varying your technique. Try running the bottle under a hot tap to warm it first, before stroking it over the length of his penis! Grab a tube of lube. You could also experiment with standing behind him, and reaching your hand around his hips to hold his penis; he could even wrap his hand lightly over yours and guide your movements. If your lover is circumcised, his glans is likely to be fractionally less sensitive; you may find he needs more lube, pressure, or stimulation. The absolute best way to tell what your lover likes in terms of hand jobs is to learn directly from him by watching how he masturbates.
