That's really tough. It is so hard to get viewers to jump ship to a different platform. Personally I don't have any faith in it; if I get some crossover traffic that is cool but I don't have any expectations. Makes it simpler for me to post to social media and other platforms, because I am not stressing about how many views or subs I get.
Basically I create content recycling my footage or using unused clips from our videos and I post those to social media and other platforms. It might not get me subscribers in bulk, but it does provide a fun experience for current subscribers to become more engrained in our content. That is the real value I see in these other platforms. Helps to turn fans into superfans.