You already said it works. If it works keep doing it.
Im in the commercial sealcoating business. Everything i do is essentially "door to door"
I go into businesses who werent thinking about their parking lot, find someone with papers stacked on their desk a mile high in the middle of 100 other things. And then I have to get them to stop what they are doing to listen to someone talk about something that didnt cross their mind before I walked in there.
Its not easy. You get a lot of rejection. But it works. It works better when I put my brochure on their paper filled desk than if it comes in the mail and ends up there.