There is now way around developing a solid service motion unfortunately. The first thing you need to work on is a fluid motion, which basically means that the racket does not stop. Think about a baseball pitcher or a quarterback throwing a football for example; it is one continuous motion without a stop in it!
the good news is that you can work on the serve by yourself without a partner as much as you want!
I have a video tip on the fluid motion with a helpful drill. You can check out if you sign up for the newsletter on my website. It is part of my Top5 Video Series
Hope that helps