Getting references after a company closes after 18 years as a teaching assistant

My manager was laid off too and I am unsure who to use as a reference. I worked as a teaching assistant before this. A colleague offered to vouch for me. Who did you use?

Ask former colleagues and supervisors in a short message and give them a summary of the job you are applying for.

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.