Slow and easy wins the race - or rather, the dragon taming ;)
If he's been with you a long time, then he should already be at a low level of stress. Just to make sure, get down on his level and check husbandry - are temps right? substrate OK? plenty of room in cage? Things to do? Are the other household pets staring at him constantly? Is he in a room that's constantly noisy/active/busy (which can be stressful)? Just look at it from his point of view and make sure everything is cool on that level.
Make sure you're not wearing strong cologune, perfume, or hand soap. Also make sure "scary" flashy things - watches, bracelets, shiny rings, etc - are at a minimum or removed. After he's taking treats from your hands, then make him come get them from your hand (set a blueberry on your palm, etc). You might consider just using one primary person while taming, so that all movements and ways of doing things remain consistant.
Then, start off slowly. Offer treats from your fingers - blueberries, mango, etc - and teach that the hand doesn't always reach in to try to pick him up, but rather is around sometimes for good stuff too. If you get bit do not jump away, scream, or otherwise startle the dragon. Once they figure out biting is not getting them anywhere, they'll give up.
Take it slow like this for a week or two, then go up a notch. Remember to *always* come from the side when reaching for the dragon, not the top. Predators would come from the top. While this is hard in a top opening cage, its possible if you go slowly. Reach in and scoop the dragon up, holding fingers under the tummy securely. Any flailing will just freak the dragon out, so be very supportive of the tummy and legs. Sometimes, if you have thinner hands (I'm female, my hands are kinda thin by comparison to my husband's) it can be hard for them to get a secure grip. A pair of thin gardening gloves or a wash cloth is very beneficial in these instances. Once you have the dragon, hold it steady *in the tank*. Don't scoop him out yet and don't put him down until he quits sqirming. Once he's being nice, put him down and/or offer a treat (wax worm, blueberry, super, whatever he loves). Reinforce good behaviour just like you would when training a dog - use name frequently, calming voice, lots of "good ", stuff like that... while it may sound hokey to do that to a dragon, it can help get them used to your voice and your movements. Keep sessions short and, while not frequent, several times a day. The point is to continue to reinforce human = good. Once the dragon is consistantly being cool with the in tank holding, feel free to move it out of tank. Make sure you're not at a height that a fall would hurt the dragon, as they can be jumpy.
Once the dragon is just fine with the primary caretaker, its time to add in a few holding sessions from other members of the family. Kids should be seated when holding the dragon and a parent present as kids startle as easily as the dragon, and the combination could be troublesome unless both are calm. The washcloth meathod of holding works extremely well with kids as their little hands have a easier time holding them in that and not getting shredded by the side spikes or nails. Reiterate to *not squeeze* with the younger kids, as that can be a quick reaction to the squirming.
Hope that helps!