The practicalities and advice for starting anal applies equally to male sphincters as it does to female ones. You probably want to get yourself some latex gloves and lube, then some male anal toys and experiment with those on your own in the bedroom first. Cheaper than a punt too, but if you still want someone else to do all the work, if it was me I'd go for a SP who provided prostate massage first to see how I got on with that.