Well depending on your GF Limits and comfort level....

Get Her to give you Head,,,,,, then start jerking while recieveing (gental of course),,,, and give her a mushroom Stamp,,,

just watch out for her eyes when you blow...

Honestly you need to not look here for the answers but look inside you and your girlfriend... no one here knows you better than her right? So theres where you should be looking...

kd