My first time that we were with another couple I was nervous, a bit drunk, and to top it off, I was tired because the evening had gone on kind of late. My performance simply was not there. This actually seems to happen quite a bit and I know the frustration that had to have been going on.
The second time I vowed not to let the nerves get to me. I stayed off the alcohol 100% and that helped. It was still difficult for me to get there because I am not used to condoms but eventually I did. I realized that even then the nerves were slowing me down. I think I'm going to be a lot better here on out on not being so damned nervous.
I would simply have to give him the same advice. Try to relax. Lay off anything that might make performance an issue.
I don't know how much this helps, but at least if he reads this he'll know that he certainly isn't alone, and yes, it gets better.