The only possible problem for you, going with Cost Plus, is that the job can drag on forever with the GC making weekly invoices for the work being done.

I sent them a spreadsheet detailing all the work done & also invoiced them for an amount over what their deposit covered (not a lot) to further drive home that I was fully aware of what they'd done, without actually coming out and saying so.

If you did, it would be hard for tenant to argue.I'm going to be doing a turnover at the end of this month, and I'll be charging the tenants the exact cleaning fee backed by work invoices.

@Mike H.Agreed, we did not pay the last invoice until he sits down and resets expectations with us which he has yet to do. 

As an alternative, the judge would have considered any payed/invoiced repairs as evidence so if i would've gotten the repairs done and payed for them, he would have awarded me the costs.4.

Do you send them e-mail reminders, or mail them an invoice for that matter, or just hope they remember?

You forgot to add, "and now that that's settled, here's my invoice." :) 

We've used several in the past few years and there seems to be no happy medium between a solo plumber who won't send invoices for two weeks and the giant company with high rates.

They shut off the water at the street, went into the crawlspace (about 5 feet in) cut the CPVC pipe, put on a shark bite, and handed my wife an invoice for $238.What I am finding is that as I go through these painful early projects, I'm slowly building a list of quality, reliable, cost-effective service providers. 

It's tough b/c I have a property management company collecting all of the rent checks and sending me monthly statements, so I don't need invoicing etc like many online bookkeeping services offer.