Any tips on masking a 72 dart grill for paint?

I have used a thinned grease and a small paint brush in the past. After it dries you just wash it with dish soap and VWALLA! An old neighbor that was a body man showed me that trick years ago. Doesn't always work, but in small areas that are difficult to mask it does a pretty good job! I use it to mask small stickers & labels also.