Update -
It's been while but I wanted to post updated results. I landed my first deal in May 2019 from door knocking. It was a pre-foreclosure. I bought it subject 2 (wasn't even trying to buy sub-2 but that's just how God works) and flipped it and made a net profit of $56K. Part beginners luck but mostly, in my opinion, a blessing from God. I'm still in contact with the sellers to this day. Since then, I've continued door knocking while also acquiring deals from wholesalers and relationships built at my local REIA and a Bill Cook/Pete Fortunato "What Box" seminar in Atlanta.
Between cold calling, Wholesalers, MLS, Relationships, and all the available ways to acquire leads and properties, I still prefer door knocking. In many ways, It's terribly inefficient. However, there is no substitute for face to face human conversation and interaction. Even during COVID-19, it works. I knocked on 7 doors this past Thursday. These were VERY targeted doors with high-equity and other indicators of being strong possibilities. From those 7 doors, I talked to 3 people face to face, received a text message from 1, and a phone call from another in response to my hand written notes left in their front door. I don't expect that I'll buy any of those 7 homes. However, compared to mailers/cold calls/etc, the response rate and contact rate can't be beat.
Door knocking is fun. I enjoy talking with folks, have learned of off-market opportunities in the neighborhood that I wasn't targeting, and 100% believe in it as a method to get into the game. It's time consuming but worth it!
Good luck!