is there a trick to make smooth stone?

don't bother with the blast furnace, it won't take stone at all, only ores and metal stuff. normal furnace or nothing.

furnace twice. cobble goes in and comes out as stone, put that stone straight back in and the second smelt is what gives you smooth stone. it catches everyone because stone already looks like the finished article. line up some fuel first, it's a slow burn for what you get.