I have Pixel-x86 running off the live USB (made with Unetbootin -- Startup Disk Creator complained about an invalid version string or something... moving along) and it is doing a decent enough job on the 15+ year old ThinkCentre A21 that I picked up years ago for parts for $5 (add the cost of a new hard drive and the total setup cost me about $50). This is a great recycling opportunity.
I am helping with setting up a Pi in my daughters school - the biggest problem was that they don't have monitors with HDMI. The focus is on using the Pi as an extension of hour-of-code activities with things like Scratch and Minecraft Pi. The potential for repurposing old x86 machines to serve this function is huge. Even the experience for them to install an operating system at home - an experience that has become highly mediated - will let them appreciate how hardware and software work together.
As for some tips: to get it to run from the USB, you have to go into the IBM BIOS and set the startup sequence so that HD1 is ahead of HD0. The USB drive is not assigned to the 'removable media' category as you might expect - that is appreantly for the old floppy disk drive (very cool to still show that to kids. I have no idea where to get them now though.)
I read in the announcement that the possibility of getting the x86 version of pixel to 'install' might be considered in future. I am going to post separately on that point, but I mention it here as well: having to run off a USB or DVD in a school setting means someone has to constantly make sure the OS doesn't take a walk. Also it means deploying a setting where the budget is shrinking and Google Education is getting all the attention, I have to do stuff under the radar out of my own pocket. I think I could scrounge up donations of ancient x86 machines pretty readily (although the desktops are becoming harder to come by as pretty much everybody above a secretary now gets a laptop... and those tend to die from other problems - screens principally - long before the hardware is 'give away for $5' obsolete.) However, if I had to pay out of pocket for each student to get even an 8GB flash drive... well, it's not going to happen. (Just like they all have to share the same SD card on the pi).