Well my advise is the following: Ask yourself "Why does one comment in the first place on steemit?" and then react according to that.
People on steemit comment to:
1.) Make money from their comment's upvotes (so they comment on whale's videos where there are people to vote their comment)
OR
2.) Answer a question you asked.
OR
3.) Ask you a question when they think you can teach them something.
OR
4.) To form relationships on the platform.
OR
5.) To troll

Ideas:
Well you don't want 5.).
Also Number 1.) seems not possible for a minnow except you attract them on the money thing maybe by buying a few Steem/SBD and making a contest/challenge. This WILL get you replies on the content video, but also many will start commenting your other videos and subscribe because they don't want to miss your contests.
2.) Is the first you should try. Ask people things, but not ONLY in the video like "What Altcoints do you prefer and why?, please tell me in te comments", make a whole video out of it with the question bein in the title and thumbnail already, so people even click your video to comment in the first place. So instead of making a video "My favorite Altcoins" and asking people within the Video, make a Video What are your favorite Altcoins an tell the in the Video which ones are yours.
3.) Simply be good on your topic, show people you are professional and experienced (present facts) on your topic.
4.)Is something everyone wants, and the most powerful point. So if you did 1.) 2.) or 3.) always reply AND upvote to comments as much as you can. Try to save upvote power to reward comments. Nothing will bring you more comments and bring you back the people who once commented, than actually showing and rewarding people for doing the work to write real comments. No matter how small the reward and your SP is, as long as it is not 0. If I get rewarded i feel like it mattered to you and it is worth to comment again.