I've never used that command, so you might need to experiment with it a bit, however, I can tell you how to get to the autostart feature in Budgie, if that helps. Start with a right-click on the desktop, and select Budgie Desktop Settings from the context menu that appears.
Autostart is at the bottom of the list on the left.
Click the + sign to add an applicatiton to run or a command to excute.
Good luck with it!
EDIT: If exact timing relative to other startup events is critical, I can't help you there. But it will be really easy to give it a try, and see whether it works for you.
