When revegging, think of pruning your roses in December. Take the harvest, but leave a little green growth toward the bottom of the plant. You don't need very much green, just enough to get started again. Then turn you lights to 18/6 to start the vegging going again. The new growth will start in about three weeks and will look very weird. The new leaves will start growing out of their weirdness and start growing normal again. Once you have a nice bush going again, you can take the cuttings and start growing from clones. Continue vegging the plant until its reached the size you want, then go 12/12 again ... and wait for the next harvest.
Vi