I don't have a Jackson but if I did I would hand feed him the same way I do all my other chameleons. Just hold the feeder up where he can see it and allow him to take it from your hand.
90% of what my jackson eats is hand fed. I hold the feeder in my fist, hold the fist in front of her, then open my hand. She is very used to this and knows what to expect. She just aims and snatches it! It may take some time for your cham to take the feeder. Just remain very still, and after awhile of doing it they will become used to it.
I do't have a Jackson's. But i skipped a day of feeding with my Veilied. The next day he handfed like he does it all the time. So try skipping a day of feeding and see what happens.