Lyra sells a liquid stylus cleaner called the "Lyra SPT Stylus Treatment" that comes with a brush (you can get it on needledoctor--I've used it and I like it) so I wouldn't think Lyra would void the warranty on their cartridges for using that, but I don't know about Zyx or any other manufacturers.
I also use an Onzow Zerodust to get the dust and grime off of the stylus. Works similarly to how people describe the magic eraser (you lower it vertically onto the surface and then lift it back up) but it's a soft, sticky pad that the dust and grime literally sticks to. I've had good success with that too. It's about $35 on ebay.