My general rule is I upvote replies that offer anything thoughtful and I check out new followers to see what they post. If they seem like they're genuinely engaging I upvote the first post I find interesting enough to finish and follow back.
I tend to be growing a good source of content to follow and I don't really get much junk.
I like this way. Feels way more organic. I do the same and I try to answer everyone unless they have a generic answer, then I am not interested. Haha