with my older pax, I found that if I had residue builing up, I just made sure I had an empty oven, heat up the unit and swab the warming oven (on low heat ) with a dry qtip every other day or so kept that hard brown residue from building up, and around the top edge where crumbs would build up. Only took a few seconds, and if the air path is also getting some build up, while the oven is still warm, I would push a dry pipe cleaner in there as well and most of the oil residues would just wipe away, key here is warming it up first to loosen up the oils and doing it frequently, say at night when you are done using it for the day and ready to charge it. It's a quick process that buys a little time between the iso cleanings. If you wait for a week or longer, you will be constantly cooking older residue to the oven as you vape new loads, so the longer you wait, the more work you will have to get it clean.