From my narrow point of view of Ventura County millennials that aren't in tech or a liberal waitress, any young person with a good head on their shoulders will be packing up and leaving soon. 

"Many people profited from the crisis in our country," says Raquel Teles, 29, heading to her job as a waitress on Madrid's Gran Via avenue.

Bandit signs (your city may be strict and take them down, put them up when city workers are not working and put them in front of a Church,Walmart or any other high traffic area because you will want full exposure) Craigslist ads (Be very consistent with these, 1-2 a week) Business cards (Very very beneficial if you give these to waiters or waitresses or people you know and give them a nice referral fee.

Its best that you bring a few dollars in cash so we do not drive the waiter/waitress crazy with splitting the bill multiple ways.

I felt so bad for the waitress I left my normal tip and gave her 10 bucks for the French dude.. :) ...

How do you handle getting applicants from waiters/waitresses and other jobs that are partially/mainly paid in cash?

OK dude :-)It's extremely easy to find engineering jobs these days, including bartender and waitress also easy to find job. 

They leave and say "OK, we will think about it." 10 minutes later she calls "I want the one with the attic, I'll pay all cash, I'm a waitress"Rent = $925I connected all the dots!

expecting the waitress to come back and give you a refill. 

I grew up on welfare for the majority of my youth and knew nothing about finances so when I got my first job I spent it on all the things I could not get from a single mom with 5 children and a waitress job at a diner.