Hello. I have a full size pick up and this weekend I was doing a basic maintenance wash and noticed a hard substance almost around the entire truck. The past two weekends I went to a masonry yard to pick up some stone products and it's the only place that I could have picked up this dirt or whatever it is on my truck. The lot is extremely dusty. Does anyone recommend a product to remove this? I did use a clay bar and it does seem to work somewhat, but the tailgate is really bad and I am wondering if there is some sort of degreaser or solvent that I could use on the paint. The substance on my truck seems like it can be removed by using a finger nail, but you really need some elbow grease and I am afraid that I may really damage the paint. Thank you in advance.