No problem...glad I can help.

When you practice, you have to practice the way you plan to perform. You say you can play the song easily and sing it easily...and that's great, that's step number one! Now you need to practice putting to two of them together. It's a separate skill.

I know it's hard. I sing backup in my duo and never sang and played prior to being in this duo. When I first tired, it felt horribly awkward!!! Over time, and I don't think it took too terribly long, I was able to do it.

When I'm singing, I'm mostly strumming chords. Playing a riff or fingerpicking would be much more difficult. The closest I come there is Already Gone by the Eagles. I can play the riff and sing the chorus. That took some practice.

Anyway, I would suggest you now only practice this song singing and playing together. When you make a mistake, play through it. You forgot how a verse starts, just keep strumming the chord you are on until it comes to you. If it's a song other folks will know, you could even say into the mic "anybody know how the next verse starts!?!?" It will get you a good laugh and you'll get started again. Turn that verse into an instrumental if you have to. Do this in your practice if you get lost or messed up...think of it as dressed rehearsal.

Practicing both together will help your brain tie the two together and wire what your hands are doing with the words in the song. You may get to where you can't sing the song without a guitar in your hand...my duo partner is that way with some songs.

Hopefully some of those random thoughts and ideas help you out. Good luck!!!