Yellow Letters are next on my list but I'm still trying to get a grasp on this method as of where to target and how that effects my response rate, hand written letters or using a yellow letter provider, and who someone would recommend, etc.

I'm not saying purchase their management products, unless you want to, but check out the pill method or replace your mortgage on youtube). 

Depending on how I do with this method, I am open to flipping in the future.

This method is called wholesaling and it does not require any money nd it is something that you can do right now.

It took numerous phone calls from my agent and myself to random people in some outsourced office halfway across the country and weeks of stress to finally get the loan closed (and only because the seller agreed to an extension at the last minute).

I would love to be able to use the BRRRR method to get started because I do not have any money for down payments, rehab, etc.

Even if you have money to purchase, you may want to start out by wholesaling (finding a property you think is a deal, and reselling the contract to purchase the property to another investor).This method is usually marketed to people who don't have $ to invest on their own, but it is the best education you can get.

I'm very curious to see what your answers will be.Even if you have no proven method I would love to hear any and all of them.Smaller PopulationResidential - Bandits signs (If permitted), Direct Mail.Commercial - Direct Mail, Driving for Dollars.Larger PopulationResidential - Direct Mail, Newspaper Ads, Office Building.Commercial - Direct Mail, Direct Call.

What would be considered the most logical method to use in this situation?

Many investors use this method but have not been around  long enough to experience the down side.