Get a bearing with removable shields so you can clean and relube easily. I use a light amount of grease with a squirt of tri flow. I do this procedure every few race days. I have more important things to do at the track than maintenance bearings. Also, spraying in a lubricant at the track almost always just pushes dirt in that is around the bearing anyway so it does more harm than good. A bearing manufacturer sends them with grease for a reason imo