This is good triage. For phase 1 (as you said), you need to stop the bleeding. This article said illegal entry is off 53%. I've read others on FR that it's off 70% and 97% - the higher number was specifically pertaining to Haiti, though, IIRC. Either way, the pendulum is swinging back.
No way of measuring those that self-deport, though I'm loving all of the sob stories in the media. I figure that media hysteria works in our favor, for once.
Next? Sanctions against employers. Removal of welfare bennies. Tax remittances back to Mexico. Take away the incentives for coming here.
I might even argue that a wall might not be necessary, with the correct enforcement of existing laws and selective application of new ones. Wonder if it's another misdirection by the Trump team....get everyone looking at the big shiny symbolic thing in the right hand while the real work gets done by the left hand behind the cape....
A wall may slow down the drug runners and terrorists.