This will require three items up front: 1) a prebuilt TechUSB to give to the client ahead of time, 2) a remote management tool able to run on Linux, and 3) a means to direct the client.
Authenticate TechUSB with TechSuite Creator (found on the downloads page). Once this is done and the drive is set up, give this to a client. From this point, the client will need to be walked through how to boot into a USB. Once the boot up is complete, remote management software should be loaded. Tools like GFI Max, Kaseya, NAble will do all of this automatically if set up properly. From here, manage remote monitoring and perform the preferred diagnostics.