Screen Sharing Software for Users

I have several users who have raised issues with my software that I'm having a hard time understanding. Others have floated thoughts about how a competitor does something better and they want to show me. I'd love to get users sharing their screen so they could walk me through specifics, but I'm unsure what software I should steer them toward.

Keep in mind that some of my users are on the older side. Asking them to install something involves a lot of hand-holding. I'm happy to walk users through the process, but I need it to be easy. I'm curious if anyone is doing screen sharing sessions with users, and if so, what software has worked for you?