I am looking at purchasing Multi-family properties where the numbers work, they cash flow just over $100 per unit, and meet the 2% rule, however for at least one of them, and for other in the future, I would like to utilize the BRRRR technique, which means it is very important that I know the approximate value the property will appraise for. 

It's a get-rich-slow technique, but it works very, very well.

I've read up on all sorts of techniques and I want to get started wholesaling.

I have yet to use this technique but plan to in the future .  

Are there any other techniques that you have found successful, like welcoming newbies?

Also check out Seth's interview on youtube with an investor from texas named Karl____  That is filled with different tips and techniques for selling and buying land.  

Its a nice scare technique 

Some possible sources:-Wholesalers finding off-market deals and sending them to their network of all cash buyers-REO's-Short Sales-For Sale By OwnersYou'll find plenty of people here on BP who use these techniques to find, rehab, and sell properties.

Best technique to market or how do I find investors who look for other individuals to invest with them? 

I have started using this technique and it has helped my direct mail gain recognition and also i have found motivated sellers through my skip tracing and cold calling efforts.