What will stick to porcelain?

I want to put a tile mosaic in my sink. It looks terrible and I dont want to use that spray on porcelain repair that's for tubs and sinks. The overflow hole has rusted through so I want to plug it, cover the hole completely and mosaic tile the bowl, leaving just the drain hole. I can't afford to rip out the counter tile(the sink is currently tiled into the counter) I have tried ruffing the sink with a piece of heavy floor tile, coarse sandpaper and a putty knife and applied thin set mortar to a small section but most of it scs off fairly easily. What can I use to ruff it up enough to make the mortar, tile and grout stick permanently? Then do I use grout sealer or do I cover the entire mosaic and grout with something else? Is this project even possible as a permanent, pretty and different repair? Please help me! Thank you very much, your help is GREATLY appreciated.....dussti