A little secret about contractors: good ones screen their potential customers just like a wise real estate investor would wish to screen their potential tennats.
first things first I wouldn't tell any contractors that your an investor and that you have a ton of work you can throw their way. Literally contractors hear people talk like that all the time and 90% of the time they're blowing smoke to try and justify that they should be charged less than a "normal customer". Also I put emphasis on not mentioning too much about what your doing: alot of contractors want little to do with investors and flippers. Not an ideal demographic as a customer for many contractors. Less info is more sometimes.
Also alot of people look for the "free estimate guy". That guy has no obligation to give you an estimate if he doesn't wanna work for you. Pay for a consultation and then the contractor will be obligated to acutally give you a quote in a timely matter.
My last advice is that sometimes people try to look for good, fast & cheap. You can have 2 of those when you're dealing with contractors. Good & fast will cost you alot because you'll need a great crew of workers making top $. good and cheap will take longer because you'll be treated like a fill in job/less important than other jobs they might have going on. Fast & cheap quilaity will suffer because its a rush to get the next payment.