I originally was thinking you meant T slots so disregard the part about lips in my original post. The part about just gluing sandpaper on a strip of wood still applies. I have a set of different sized dowels with 80 and 120 grits glued to them for rounded grooves, ogees, etc. Works well and costs virtually nothing.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.