In my experience, metal to plastic friction was the main culprit of gritty feel in NEW Alps black switch in Dell AT101W. Most of the gritty feel went away after lubricating the metal leaves with silicone oil(I used Victorinox multi tool oil). It was about two years ago when I first tried lubricating and silicone oil was only lubricant I had at the moment. After two years of spotty use, it works just fine. It didn't get sticky and dust accumulation didn't seem to cause issues.
Here is where you should put some lubricants. I used oil dropper and smeared some oil on the metal leaves.
Also, the Alps switch housings are ABS plastic which is known to have friction issues. ABS plastics degrade when rubbed against and the friction becomes an issue after some time. So, I think it is important to put some lubricant on the sliders where it touches the switch housing. See red arrows in the below pics.
Here is a link to lubrication wiki I maintain in Korean. KBDMania lubrication wiki
If you know Korean you might find the information useful, not so much if you don't.
I tried Krytox GPL100 on the metal leaf and it seems to work pretty well without changing the feel that much. If you want to try some exotic / top of the line lube I would recommend you try Krytox GPL100. Search Krytox GPL100 in ebay and you should be able to get some in small quantity. Victorinox multi-tool oil seems to work well too, but it seems to change the feel of the switch a bit. The silicone oil makes the lubed switches a bit softer. I personally like the softer and more dampened feel, but it is my personal preference. Both oils are pretty easy to get, so you might want to try both and see what you like.
I hope it helped. Personally, I think lubrication is a MUST for Alps switches. I cannot say the same for Cherry switches, but it certainly feels nice to type on lubricated Cherry switches.