I think it can also just depend on the pig. My youngest, Killian, is so calm and happy with anyone! He just sits there and nuzzles you and explores your hands and arms, and then just sits on your shoulder telling you all about his day. Sir Pig can't STAND to be picked up, but once you settle him on your shoulder and pet him, he's perfectly content. President Snow absolutely loathes being picked up and held. You can sit him in your lap and scratch under his chin, but anything else and he's not a happy piggy. He's never bitten me, but he just pouts when I pick him up.
It's the same way for floor time. Killian Jones runs around all sorts of spazzy and happy, Sir Pig takes time to warm up to floor time, and President Snow just sits in a hidey, munching on hay and looking pouty. Some of them take much longer to warm up to humans, so the towel trick is amazing, but another thing I personally like to do is actually get into the cage. I know that sounds completely weird! But I have a 2X5 with a 2X2 attachment, so when I'm spot cleaning poop, I have to step into the cage (it is on the floor, so it's not a huge trouble for me) and sweep up that way. But whenever I do that, they seem to love it! They begin popcorning, running up and sniffing me, popcorning away, then run zoomies through my legs. At first they didn't seem to like it, but now they get excited when I do it. I think because my scent has gotten all up in their cage, it made them get used to it even faster due to the overwhelming human smell everywhere that they run around and sleep.
While I know that not everyone has that odd little helpful bit, something similar that you can do is just rest your hand and arm in the cage. Like I said, mine is on the floor so I usually sit beside the cage on my laptop (what I'm doing right now, actually) and chat with them. I'll rest my arm in the cage, and as they walk by they sniff me and keep going. It's a smaller scale version of me being in there to clean. Basically, it gets my scent where they are, and makes them comfortable with it.