I have a Legend HCx, and I use a slight variation on what saturn has said above (although I am now going to try what he suggests, I suspect it may cut out my GPX modification step).
In bikehike, plot the route using follow roads (occasionally turn this off for sections when google won't follow the route as described (eg off-road path sections etc).
Add coursepoints (using Generic type, named to describe the turn, similar to saturn eg 01-L 02-R) etc) for each routesheet instruction.
Dowload to PC as a GPX TRACK from bikehike - This GPX contains a track and a set of named WAYPOINTs.
I manually edit the gpx file in a text editor to change the waypoints into a route of ROUTEPOINTS. (mainly a find-replace on <wpt </wpt to <rtept </rtpt, and wrapping them inside <rte> </rte> tags
If a route involves loops or recrosses itself, split the route into more than one, avioding crossing.
Open the modified GPX file in Mapsource.
For the track, modify the properties to set the colour to a nice visible green, and limit the trackpoints to 500.
transfer both route(s) and track into the GPS from Mapsource in one step.
On the GPS, set the track to be visible.
Select the route (or sub-route if split) and navigate (off-road)
You get a nice highlighted green track, beeps and pop-up instruction prompts just before each route instruction, plus you get the 'distance to next' feature giving you the "as-the-crow-flies" distance to that next instruction.