You might be over thinking it.  If you just crack the garage door open about 6" and stand back 15-20' and roll cast right at that opening it will give you the motion.  Once you can consistently hit the pavement directly below the door with a low trajectory then do it harder and harder.  Honestly, you could probably stand in the garage and cast out, would be a little warmer...

 

Might scare the crap out of the mailman!

Nah, I'm good. My mail person will not get out of their right side of the car steering wheel car haha.