A oscillating spindle sander works very well, but could be considered an investment in your future as far as tools go.... I assume you have a guide line to go off, body putty , file, a range of paper, and a pile of dedication can get the radii correct. When its perfect then use that as a template to make new pieces with your router....However If its not too bad (and with realistic expectations) You could prime sand, prime sand and work it close enough to be covered by a "T".