I'm no expert....but why not just use the sust along with the test e and deca at the same time? Doing so will give you a good front of the test, and you will also be taking some good advantage of the prop that's in the sust. It's not much....but it will help. Primarily, use it to front. Prop would be better, but sust will do.
How much test are you planning on running?
I would just run sust till its gone like 2 ml 2xwk then switch to Test E when its gone. basically what V said. the short esters will give you the pop to get the ball rolling then when you add the E you'll be running hot already because of the long esters in the Sust and you wont have to wait for the Test E to fully kick in as it will already be fully active