I use something like SkyVector to plot out the route; say VOR to VOR and fly over a couple of airports, low and slow.
Then I write down the waypoints on a piece of paper, or I'll have SkyVector up on my laptop (the "electronic kneeboard"). Next, I'll set the 1st waypoint with the GPS, and fly to it. When I'm about 5nm away from the 1st waypoint, I'll refer to my list and plug in the ICAO code for the next waypoint,
but I won't hit "enter" on the GPS until I fly over the waypoint.
I'll keep on doing this from point to point until I get to my destination.
SkyVector's Flight Plan feature comes in handy... you can almost use it as a moving map display to track your flight, except your bird isn't shown on the map, of course.
Alan