I have had a couple of "iron incidents" and because of this I always buy an iron with a shiny sole plate so I don't know about the Mr Clean eraser tip for you. I have used this and it worked wonderfully for me. All the gunk from starching and ironing came off.
The other thing I did to get plastic off my iron was to freeze it. I didn't have room in my freezer so I sat it on a bed of ice cubes. This freezes the plastic and gets it brittle so you can peel it off - chip it off. I got my iron clean with this and I had a lot of plastic on it. Got the tip off the internet and it worked. You might try it with yours. I had tried getting the iron hot and rubbing it back and forth and it only made it worse.