How often and what should be used.
I prior printers I have had success with Sewing machine oil and or Hair Clipper oil.
I think there is a lubrication video in the support section of the website. The inner rods on which the carriage bearings run should get teflon-based grease (like the one that comes with the printer). The outer rods use bronze bushings. I think the Zortrax tutorial says to grease those, but I've read elsewhere that bronze bushings do not need and should not get grease.
Thank you
Do yourself a favor and grease also the bronze bushings. Dust, dirt and also the fumes of the molten materials condense onto the rods, the grease absorbs that all, turns grey or black, then its time to remove it and use new grease. I use a lot of grease right beside the bushings that act as a "plug" and prevents dirt ingestion. I am convinced that this will increase the lifetime of the printer.
regards
Andi