I used to clean them, but don't bother anymore. But what worked great for me was to use a paint brush to swab the gobs of grease up. Wipe with brush to get the grease, then scrape the brush on a scrap piece of cardboard. That would get rid of the messy stuff, mainly the old grease that pushed out when greasing the FEL. If I really wanted it clean, I found that the best and cheapest solution was to put some diesel on a paper towel or rag, and use it to cut through the grease and wipe it clean. Diesel is cheaper than any degreaser product you are going to find in a bottle or spray can.