it is oil isn't it? and not brake fluid? ie not eaten into the paint?

Claybar's are very easy to use and the benefit is that you are removing the grit and grime and not dragging it around the paint as you polish as the shite sinks into the clay.

In short, wash the car to remove excess dirt, then use the spray lube the claybar comes with and wet the panel and with the clay car softened up (pop in warm water for 5 mins if in cold weather) rub back and forth across the panel, and as you do, you will feel the resistance become less and less until it is gliding, then move onto the next area, always keeping the area lubed up. Dry off and polish up.

The bonus to it is that after you have done it the finish feels silky smooth and polish will go on and come off MUCH more easily and with better results.

Well worth doing and unlike t-cut, it is not removing paint, just taking out the shite from it.