Never pay your installers an hourly rate, an hourly rate is for your employees only.
We usually tallyup how much material it will take up, email the job proof to the installers, how much square feet it is and ask for a square foot price.
Charge by the hour and it will take twice as long to complete. I can do a 10-ft by 10 foot wall graphic in half the amount of time as our normal installer, and do a better job. If I got paid per hour what that guy got paid you can bet I'm taking my time instead of working my ass off.
There's been an occasion where we tell an installer where we need to be per square foot because it is a budget job, and most of the time they can work with us, but that's because we're not haggling the price on every single job and send them a lot of work.
There's one installer who works for us, we were doing about 1500 square feet of wall graphics. I think he ended up charging 2 a square foot, which we considered really cheap,and he finished it in under one day. So 3 thusand dollars for 8 hours of work... At your $50 an hour rate you would have only got paid $400.
And would have laughed in our face if that's what we offered him.
So while you can look for a $50 an hour person, you usually will end up getting bottom of the barrel when you're using a contractor...