The best way I've re-vegged is by leaving 4 or more full-sized fan leaves attached to the trunk and put the plant under flourescents until it reverts back to veg.
Somewhere down low in the trunk you will eventually see some micro leaves growing out of the side of the trunk.
When you see those leaves, you're on your way.
It may take a month to get to that point, but once the leaves start growing back they will grow quickly as there is already a good root system below it to help it thrive.
The main things are to not over water as the water uptake will have slowed to a crawl with no vegetation to use it.
And be careful about burning the new leaves.
Once the new leaves have formed a carbuncle it will start throwing out more and more leaves which all will become branches.
I started my current re-veg at the same time I germinated seeds, and if I had put one more month on the re-veg it would have been equal in size to the plants vegged from seed for 60 days.
So, overall, re-vegging will need about a month extra of plant growth to get it "full sized".
Re-veg's make for excellent mothers, too: very bushy with lots of branches to take clippings from for cloning.