You can build the draw over several exchanges, it doesn't have to be something that works in every single exchange. Boxing is all about teaching and learning. You're teaching your opponent what you do and you're learning what he does about it. If you back straight up twice, you're probably going to back straight up a third time. So backing up straight until your opponent LEARNS to follow is the time that you use lateral movement with some counter punching.
If you TEACH your opponent that you always throw a double jab, when you go to a 1 - 2 he'll expect a 1-1 because that's what he LEARNED.
See how that works?
If you're always coming forward, your opponent will learn to back up, plain and simple. You need to stand your ground a few times in order to get your opponent to respond. A good way to "inspire" your opponent to come in is with pot shots like the step-in-the-hole jab. When you hit him, he'll feel the need to retaliate... profit.
I'm good at getting guys to come forward, but I'm forced to defend a lot because of it. When they tire out and their hands drop before they swing I just send straights out. They LEARN to keep their hands up... so I advance and throw some offense to shake them up and help them forget. Rinse, repeat.