Leaderboard

That grease will eat any rubber in short order. Never use common grease on brakes. You'll need to disassemble and clean it all off. Caliper grease only, like this one here. The only places that need grease in brakes are under the hardware (yes, you read that right, between the hardware and the caliper bracket), in the slide pin boots, and on the backs of the pads to reduce noise. The caliper piston boot does not need grease. The backing plate can use grease where it contacts shoes, but I think you are misusing the words "backing plate", so you do not need to worry about that. It sounds like you did not touch the pin boots, so get yourself some brake clean, take any grease left off, and put a light coat of caliper grease in the above mentioned places. Again, be careful with the nomenclature as it can be confusing on a forum. This is a backing plate: These are the brake pads, and the top two images here are just the back of the brake pads, not backing plates: