Here’s a tip. never count on the markers left in the classroom or training room to work. Bring your own.
I have 6 Dry Erase markers in a ziploc bag, and 10 Mr Sharpie Markers (for flip charts) in a separate ziploc bag.
The ziploc bags help keep them fresh, as does storing them horizontally.
Popart Fluorescent markers are also great for whiteboards or even for writing on glass windows if no dry erase board is available. They are kinda like paint markers but they wipe off with a paper towel.