Which spotting dye are you using? I use the Marshall's dyes (no longer available, unfortunately) and they blend perfectly with the papers I've used them with. That includes Ilford Multigrade Fiber Glossy, Ilford Multigrade Art 300, and Foma Fomabrom Variant III Glossy. This is the only spotting dye I've used that is invisible to my eye once dry on these papers. I've also tried Peerless Dry Spot Retouching Sheets and Fotospeed's DY10 B&W Retouch Kit, but both of these left clearly visible marks on the paper.
Once I run out of the Marshall's dyes (which, thankfully, could take years at the rate I use them) , I'm not sure what I'm going to use.