Bertie often eats about 8ccs in a sitting before she starts making a fuss. If I'm lucky, I can get about 12ccs into her. It depends on her attitude of the day. In contrast, I believe Willow has sucked down 15cc of critical care at one go. I don't think she even came up for air. Willow will try to pull the syringe out of my hand if I don't feed it to her fast enough. She's more than happy to take any leftovers Bertie is unwilling to eat.
So many hand feeding videos on YouTube are of guinea pigs like Willow, happily slurping down Critical Care as fast as they can. It makes it look so easy. Hand feeding a problem pig can be a real challenge. I finally got a decent video of Bertie demonstrating what it's like to feed an unwilling pig. This is about half as bad as she can get. Her worst attitude can be pretty funny, especially when she flat out says NO!
For those of you that are interested, there is a good video called Handfeeding your guinea pig that shows how to mix up the mash and fill up a set of 1cc syringes. I normally just mix the Critical Care with water. However, with Bertie, I've been experimenting mixing the Critical Care with squash or banana baby food - anything that will make her more willing to eat it!