Note my last sentance. 'preplanned'.
Any navigation exercise need a standard VFR flightplan that lists Track, Heading , Groundspeed,Weather and Alternates if required. Fiddling in flight with whiz-wheel's, protractors etc is a no go. Your heading will go to pot and compound any errors.
Make a simple flight plan, accurately fly your planned heading ,check on a prominent fix en route and then make any alterations to current heading to proceed to destination if off track. When your estimated elapsed time for that leg comes up on the clock you will be within sighting distance, more likely over the destination.
Until you gain confidence the 10 minute markers can be helpful. Mark your track using calculated ground speed at 10 minute intervals . In flight note time en route divide by 10 and pick appropriate marker, interpolating if necessary . That's where you will be !!
Joe