Lunging should be kept to a minimum IMO, no more than 20 minutes total.
I like the approach as follows, "on" being work days (ridden or ground), "off" being no work days. 3 days on, 2 days off, 2 days on, 1 day off, 1 day on, 1 day off, then repeat.
Start with plenty of walking: patterns, some poles, circles, etc. Then move on to trotting 5-10 strides at a time, in a straight line, with 5-10 strides of walking betweem (equal walk to trot). Once he's warmed up at the trot, do a few big circles or serpentines, bending nicely at the trot. Finish with some walking patterns on a loose rein.
I would not trot any poles for a few rides, or until your vet gives you the okay. I would sit the trot, with your back soft and shoulder's back, encouraging him to properly use his back and lift his front end. If your sitting trot is not good, then I would half seat, to give him free use of his back.