Installation Only Pricing Help

I'm focusing on providing installation services to local sign and wrap shops. I was wondering what a fair rate would be to charge for installation only of dimensional wall signage. I'm not sure how to charge for it at all to be honest. I'm pretty good when it comes to estimating for wall-vinyl, floor installs or vehicle wraps, and while I've installed dimensional wall signage I did it as an hourly employee and didn't estimate any of those jobs.

I also had someone ask me about rates for table-work (weed, mask, assembly, etc.) and it stumped me. So after saying "I'll look into it and get back to you on that", I spent some time researching how much to charge for something like that. I'm coming up with nothing on the research end.

The biggest problem I see is that I don't know how realistic it is to come up with something that isn't an hourly rate, and then to make it something fair enough that a shop-owner would want to pay it while high enough to be worth the time for me to accept the work. I charge a $60 hourly rate when I have to price jobs by time only: usually the price is based on square footage for installs. For something like weeding and masking that seems unreasonably high when you can hire someone at $10-$15 an hour to do the same thing for 20 hours a week, plus sweep floors, clean the shop, answer phone calls, etc. The advantage of not having to pay the hourly employee may be worth it though if you run a shop that does a lot of outsourcing for printing and/or fabrication and don't really need the extra hands while only occasionally needing to weed large runs of small decals or window lettering for 20 businesses windows at a strip-mall or the like.
Just thought I'd put it out there and see what sort of feedback I'd get.

Thanks in advance.