Good luck with your project.
Food for thought - paying equity for labor can be very expensive.
First there is the ultimate cost of the equity you paid
Secondly, because (as you mentioned) it`s so difficult to place a value on the equity (ie valuation on the company) - the company generally has to "pay more" in equity to get the needed services.
An additional consideration, is whether equity alone will enable you to "hire" the best talent available and whether you will be able to "live " with that person as a "partner" in your enterprise for the long term
The old adage says - "there is more than one way to skin the cat" and there is more than one way to bring capital into a business.
One key to success is to be sure the offer is appropriate for the stage of the company -then "match" the offer up with potential investors.