Low and zero down methods are a bit more difficult to do with an active full time day job due to being more time consuming.  

Additionally, I've also been wondering, rather than using equity to purchase a multifamily, should I be using the equity in a method I've heard to pay down and fast track the payment on principal?

You could also seek to use the BRRR method to get some or all of your money out to put towards another property.

What methods/formulas are you currently using to identify good deals vs bad ones?

Have you compared that to any other available financing methods? 

means the BRRR method wont work anymore?

With this method, you can use the "projected rental income" without proof of occupancy/renters to help you qualify (income-wise) as long as the rents meet the Self-Sufficiency Rule.

I will try that method tomorrow and see how far I can get.

I am not saying that this is the best way to go as i am not following this method myself, but it is the way I imagine it would go if I were interested in doing so and disciplined enough not to spend the income from the rentals.  

Of course use this method if you can't seem to find the "perfect tenant" to rent the property.