This trip is a bit high end but if you want to try catching Dollies....Big Dollies check out the Wulik and the Kelly Rivers. Mid Aug spawn and fish in the 15-18 pound range all day long with a few in the 22+ range.
Shoot me a pm and I will fill you in as needed.
Link:
http://www.flyfisherman.com/canada/northwest-territories/lonesome-lands-arctic-char/
