So the guy calls me up and says his grant came in low and would I do
it for 150.00. Well this guy recorded a whole CD with a friend of mine
and paid the hourly rate and so on so I assume he knows what he will
get for this and I say yes.

I haul tons of equipment...

Let's stop there :-)
You did this gig because you wanted to. You charged enough to cover
expenses, and maybe have a drink. This was your choice.

I'd say to the guy - "What the F***! This was always a free gig.
GIve me the $150 for hauling the gear. You're not employing me, but
purely for my own satisfaction, I'm going to get it as right as I can,
in a reasonable amount of time. Now, what was it you think needs
doing?"

That is, if you don't want to tell him to F*** off

The thing is, the trombone player was losing his lip as the show went
on. I went out and moved his mic closer 3 times but by the last
several tunes in a lot of passages he is playing no louder than the
ambient bleed. So a lot of it can't be fixed with gating or expansion.
The horn player came to me and said they didn't give him enough lead
time to get his lip ready for the show.


Nice one! So he only practises when there's a gig coming up?

I play piano a lot for musical theatre auditions. You wouldn't
believe the number of actors, presumably actively in the job market,
who "only heard about the audition yesterday" and therefore can't
offer a properly prepared song.