One suggestion would be if you already have a guy that you play with, enlist him rather than someone new. At least for the first attempt at this. I'm assuming that you have already discussed and are both on board with the idea.
One of our favorite porn videos is of this exact same sequence. Where the whole thing could have been better is taking more time before it was obvious there were 2 guys present. That was done when she felt 2 cocks at once. They of course rushed this for the sake of the video so they could get to the MFM faster.
One other thought but, if the 2nd guy was close in size/stature and you were quiet enough you could keep the secret a little longer. You also might want to set one of your phones or your own video camera up to record the fun so you could both watch and enjoy it later.

