GMOD movie making tips?

I am a beginner at gmod movie making and want to make one.

I cannot use fraps, i have a mac

I can use screenflow but it lags the game for me (is source an option?)

I am not a beginner at video editing though so please tell me your tips and tricks you have learned from making gmod movies

Like ADVANCED stuff, not the basics

Read up on Source Recorder and for our sake plan before you start filming.