The best strategy for that is to plant a viral bomb. Post video responses to both old and new videos that have very high number of views daily. Check a video count on day 1, then check the video count the same time the following day. This will give an approximate idea of how many views you will get daily. This strategy is best employed by watching as many new videos as possible. Then seeing which ones are getting very high views right out of the gate. This could lead to having your response video in front of 1 million youtubers. The more targeted your niche is, the more difficult this will be. Make certain your responses are very relevant, and very intelligent. You don't want to look dumb in front of 1 million people do you? Also make certain the videos you are responding to, are very relevant to the product you are trying to market.
Yesterday I started a campaign. So far I had 4 clicks from youtube. Not so good I guess. The video was very poor quality though. I had a kid from Canada do it for me, it was kind of unprofessional.
There is so much hype about all marketing techniques. Unless you try something, you would never know. So far my video campaign is a failure, got only few clicks.