My ex gf who I used to share with my best friend said on the first time we double penetrated her was: “OMG I’m going to cum all over your cocks again, you guys are incredible” she was so fucking hot
Gesturally, her head slowly tips backward, her chin jutting more and more...which tells me she is getting close to climaxing. Vocally, her moans and groans climb higher octaves, so that's another sign. Ultimately, though, her body tenses and she yells out, "Oh, fuck...I'm going to cum!" followed by "I'm cumming!" Great stuff every.single.time!
Ny lady says, "good cock good cock good cock good cock good cock good cock good co mmmuuuuaaaaarrrrrrgggggghhhhhhhhaaaaaaaaaaaaaa"