I have my chins a month now, and they are still little ones (3 and 4 months) and I dunno if we did a superb job or if I was just lucky with them, but we can handle them easily.
In the begin they acted like yours, we managed to turn that behaviour around in a week.
The things we did are simple: every night we (me and my GF) go sit on a big pillow in front of the cage and open the doors.
We talk to them all the time, encourage them with our voice to approach and gave them a big "No" when they started nibbling our clothes.
We also put our arms/hands a lot in the cage without grabbing/chasing/moving. They started to get curious and explore our hands/arms, they started to hop on/off...
By now we can put our arm in, the chins hop on, we slowly move our arm outside the cage (sitting on the floor, max drop is like 10 inch, onto a pillow

) and we can pet them. In the meanwhile they just look around and sniff without reacting on the petting (good nor bad) and when they get tired of it (usually a half minute or so

) they hop back in to the cage.
Something that I found that made them trust my hands more, is making a sort of a funnel with one hand (make fist and open up the upper fingers a bit more) and then put some pellets in.
I then just putted my hand in there, they got curiousfor the scent of the pellets, and they started to get closer to my hand. By now they stick their head in my hand without any doubts from their side, and they rest their little paws on one of my hands in between the pellet-grabbing to munch them down at ease

I advice you to use fresh pellets for this cause they seem to prefer them over the "old" ones in their feeding bowl...