Experienced ATL investors - How are you calculating ARV??

[Hayes Eiford]

I am working on a remodel currently. I have calculated a ball park ARV based on Zillow comps and reading my appraisal of the home before remodel and applying methods the appraiser used. I am in Johns Creek, Ga (North of Atlanta). What methods are other investors using to accurately estimate ARV? What are you doing in your remodel to increase the ARV?