Stretch it yourself. Start of 8mm and work your way up. I stretched to 11mm. Seems to be my limit. I continue trying 12mm but it seems to be a bit painful. I had it in once or twice, but I could not leave it in there long. In the beginning I used a strectcher, The one with wing nut on the top. every few minutes I would turn the nut 180 degrees, or a half a turn. be sure your plugs are sterile. Very important. My girl can finger fuck my dick hole up to her first knuckle on little finger. I like cumming plugged. Feels great. But I want deeper. Stretching takes a long time. Go slow.
I love watching the sound disappear inside his cock. Its simple to do, just tilt the cock towards the knees and the urethra lines up straight into his body.