Hmm well I can try to help you this is what I did with my boys and its worked well, but it really depends on the personality of the piggie, Harvey is really outgoing and now six months down the line I can pick him up, stroke him no bother, but with Artie he still runs away if I'm too 'quick' with my movements, however will be petted if at eye height with me (ie he's on a table) and has lots of veggies, unlike Harvey he prefers to be sat on my lap where he can fall asleep - i think he's a lazy pig!
But both boys now come running on the morning to greet me (or my veggies should i say!). It takes alot of time i found to bond with Artie, Harvey was easy and no trouble whatsoever.
For the first week with me I talked, nattered softly to them for about an hour to two hours a day with my hands in the cage, (I was sat on a chair whilst watching my arty program for uni) they came out and i let them sniff/walk nibble my hands - for the first two mornings they wouldn't shift! But eventually curiosity got the better of them
Then i gradually moved my hands, so they got used to the movement, and the second week i left my hands in the cage and began interacting with them holding veggies in one hand to feed them i used the other to stroke them near their ears so they could still see my hand and what i was doing
It really helps if you can put the cage (if their in one) at a height where we don't seem so daughting!
During the third week whenever they were sitting in their cosy cup I'd scoope them up to have bonding time, where I'd brush them or just have them sat on my lap for twenty minutes or so. I feel this really helped them get used to me, sitting in something that is familiar and warm
I also sat on the floor (with a book!) during floor time with them, they became less scared of how big I was and happyily used me as a climbing rock
I'd suggest over the next couple of weeks to have plenty of grooming sessions, with them in pairs- i found it was less distressing for my boys when they weren't split up!
I don't know if this works or if it's just me being barmy but i also rubbed my hands with hay so didn't smell so unfamiliar to them
I'm still working with them so it seems theirs no quick solution, but i wish you the best of luck and hopefully they'll start coming out of their shell soon, just take your time and hope they all settle in well soon good luck xxxxx
