'A lubricated gloved finger is inserted in the anus and the sac is squeezed between thumb & forefinger into a tissue held externally. The procedure is repeated on the opposite side.'
This is the first pornsite I've found in years that I'd actually advertise to swarmers. When you first load it up, it looks just like every crappy scam site out there, except that it's real. It's huge, it's updated constantly, there's no spam, no popups, and no bullshit -- and it's completely free. When you sign up through that link above and respond to the confirmation email, I make a bit of loose change.
See what other swarmers have to say about it. People love this place, so I feel fine about sending you there and am confident you will enjoy boners.