It might just be me, but I don't quite understand what you are asking.

Can you use relays to drive brushless motors? - no, they don't respond quick enough.

How do you drive a relay? - the easiest way is to use something like these (although exactly what one will depend on the application): https://www.pololu.com/docs/0J60/5.2 https://hobbyking.com/en_us/turnigy-...ay-switch.html

Can you elaborate on your question?

Paul