[stbke]

You will need: clothespins, strong string without much give, both vibes, a 30-minute timer.

First, tie two clothespins to strings and tie those strings to solid anchor points (bed posts might work). Make sure the strings are short enough that any significant movement of your torso while they're clamped to your nipples will cause them to be ripped off. Use trial and error on yourself if necessary.

Once they're well-aligned, sit up very straight, put the 7" vibe inside and hold the bullet against your clit with tight panties, and turn them both on. Then clamp both nipples and start the timer.

Every time you rip off the clothespins, pause the timer until you have them back on (don't stop the vibes during that time!) After the timer runs out, you're free to go.