Welcome to the SI101 Board and its Forums. I hope you enjoy participating. Please begin by familiarizing yourself with the FAQs, the Posting Guidelines section, and especially the Index, all found at the top of the main screen. The Index contains links to helpful informative insightful, as well as how-to articles that discuss the most common questions and concerns people ask about. Clicking on the site's Home page will provide even more information.
I recommend that the two of you read the following articles:
Male / Female Sexual Behavior--If I like certain things does this mean I'm Gay?
"Playing Ball" and How To Tips for Prostate Massage
This is also an excellent tutorial for people interested in and concerned about the how-to of Anal stimulation as well as play.
As for how popular the activity is, use your favorite internet search engine and ask. You can also go to a local adult store or seach on line for sex toys and dildos. Click on the site's Home page for more information, also.
Anal play can range between fingering outside and just inside the anus for both genders, to prostate massage for for guys, to inserting dildos, to intercourse.
Being "Gay" is all about sexual attraction, not what form of stimulation is found to be pleasurable.