I only use mugs for storing pens, pencils, brushes, etc.
This is a little one I bought as a souvenir in Portugal.
I used my Lamy Safari with Noodler's ink on the three previous EDM's, but I have to wait for the ink to dry and make sure it's not too thick before making erasures or adding watercolor. This time I tried the Micron 01, and the strokes are too broad for me. At least the ink does not smear when the pencil guides are erased, and it's waterproof.