'Learning the route' is pointless; flight simulator programs are simply nice toys and of no real value for visual navigation training.
Draw some routes on a map, then calculate heading and time.
Using a normal timepiece, start a leg at a specific time having previously noted elapsed time at visual fix points. You don't need many; if you have too many you will tend to track crawl rather than fly accurately using pre-calculated heading and time for navigation.
Complete your 'post-HAAT' check.
Work out the ETA for the first fix. Then imagine you pass abeam a little off track and not quite at the planned time (or get someone else to say e.g "OK - it's 09:10 and you find yourself here."). Practise mentally working out the corrections you will need to your heading and update the ETA at the next turning point.
When you've completed the correction (hopefully these days back to your pre-planned track rather than direct to the turning point..), allow time to have completed a 'FREDAL' check at a low activity point.
Give yourself another fix/time/position correction problem.
Practise the necessary radio calls and research with whom you should communicate. Only use the radio for a specific purpose (e.g. a MATZ crossing or clearance to enter a Class D CTR), not just because you can!
When you're confident with amending headings and ETAs, move on to practising visual diversions using MDR.
You don't need a computer and flight simulator game; just an old map, pencil and paper and a clock. Plan using either an electronic calculator, old-style whizz-wheel or flight planning software, then mentally cross-check your plan for gross errors using MDR.
Navigation cannot be difficult if navigators can do it! As well as planning accurately and flying accurately, the most important thing is probably organisation so that you have a mental plan of what you should be doing at any time. But aim to use the minimum time looking at the map / ground and the maximum time lOOking out for other traffic.