I assume you're aiming for an "inexpensive" designer because too many clients complain about design fees in the first place, and it's not a profitable aspect of printing / sign making. I get that. But being the "translator" for all the back and forth revisions / approvals isn't particularly efficient either, especially when you're in different time zones.
When a designer doesn't have experience in the sign biz (especially in a hands-on production environment), they won't know what your limitations are, how their artwork affects your workflow, production methods or costs. Nor will they share your expertise in marketing / branding / aesthetic tastes... which means you'll still be spending plenty of time getting things "right". It's less important on say, a banner or poster design... so it's not 100% of the time, but still happens quite a bit.
Over the past 24 years I've done it all. Doing all the work myself, outsourcing to freelancers, hiring part-time designers (in-house), and even developing a central hub (sort of like freelancer.com, with a proofing system, etc... contained only my listings, my approved designers, etc.)
Which method did I like the most? None of those, really.
Consider this: If you really need a designer to free up your time, then maybe don't "hire" one at all. Remove design fees from the equation and focus on what actually makes you money.
Over a decade ago I started working with local, independent designers (reputable ones that are known for their work in the community). At first I was concerned about their rates... usually $45/hour (at that time), and now about $60-65/hour... rates that are hard to get in a sign shop when so many customers expect it to be "included" in the price. Then I looked at it a different way. I can't compete with graphics designers. Shop overhead is way too high. But I had to try something. For the first several months I would bring the designer over (for specific consultations) and have him observe how I handle clients' ideas and make suggestions (obviously, as the sign guy, my suggestions are calculated with production value / methods / cost in mind). This was extremely helpful for the designer. And when the designer became more consistent in sending me print ready artwork, I was sold. At that point I told the designer to get me a box of business cards. I refer the clients to him. He sends me print-ready files and he bills the customer directly for his time. And this relationship continued to improve / get more streamlined over time. It's the best case scenario for me. And guess what? That money stays in town instead of going overseas, not to mention the additional work he sends my way from his clients (I did this with several designers, each with their own specialties). It's a win-win.
Anytime I have a job that's going to take more than say... 30 minutes to mock-up, or if it's something extra detailed, or the customer seems like they could be difficult to work with, I just tell them (professionally, but in a nutshell): Hey, my shop rate is $120/hr. You're better off working with a local designer for half that price. They can knock out your design way faster too. Here's the designer's business card. You've seen his work all over town (insert examples). He'll get you all fixed up, and when you're happy, he'll send me the artwork, ready to go into production. I can get you the better price that way (e.g. not having to hide design fees in the sign cost) and it will speed up the overall ETA. I also explain to them... hey, you need a design done, regardless of which sign company you hire. So this is the best first step.
Clients appreciate my honesty, and they always come back. I kid you not... even when we had 6 to 7 sign shops in town, I don't think I ever lost a job due to that customer taking designs to a different company (and I would know because the designer and I talk pretty frequently). Occasionally you'd have the tire kickers or whatever, maybe they didn't have the capital to get their startup off the ground, or whatever... but it wasn't my time being wasted, and the designer still got his share. I've done this for many hundreds of jobs over the years. It's great.
So that's my recommendation.