Updating liveusb persistent

Hello all.

So I decided, for my sins, to install the livecd to a USB, my first time.

After reading that you have to use persistent to save changes etc. I tried an update.

I was surprised on this new install that it wanted to upgrade 1.5GB of stuff. OK - I have a 32GB USB, so I tried.

It aborted with filesystem full. I did a df -h, and so it is.

Hmmm...Did a bunch of searches. More Hmm.

So, how do you update the livedc USB ???

I am stuck.

All pointers, clue sticks, 2x4's greatly appreciated as I start this journey.