Take your time!
I would say do little pieces, but often. Secondly, try and learn a route in small sections.
Whilst a lot of the core information has been given to learning a route. Also learn the risks associated with the route you are learning. This would be things like short signal sections, TPWS hotspots, if your network is updated with the new LED type signals-learn signals that are known as transitional (when signals change from 4 aspect signalling to 3 aspect, low rail adhession areas, shunts possible and the risks involved with that, areas for potential read across, stations with a risk of a SOY SPAD.
When it comes to learning crossings, don’t stress out about learning every foot crossing. Just learn the important ones and who controls it. (CCTV, UWC, AOCL, ABCL, AHB, etc!)
Don’t forget the local instructions from your Sectional Appendix.
You’ll also need to learn which signaller /workstation controls which area. Some TOCs, this maybe very straight forward, but on a route from one major city/town to another this is a little bit more complex.
Last and but least, don’t forget about route learning the depot! Again, shunts, risks, local instructions from both the Sectional Appendix and your TOCs instructions.
There is a lot to take in, it takes time but don’t waste that time. Ask your DI and mess room colleagues lots of questions. Things to consider, don’t assume your DI will tell you everything. Some do, some don’t. Some are very good at testing your knowledge, some won’t say nothing; other than last nights football.
It helps to have more than one DI throughout your handling if possible. This is all down to your TOCs constraints.
Filming the route...be careful with this, you could end up with the sack for using an electronic device on the move. Check with your TOC first. If your TOC is passionate in your development they may have videos or an online database with your networks routes. You maybe even more lucky if they have a video of the most common shunts made.
If you feel overwhelmed, then have an easy day and visit stations. Learn where things are in your major connection/terminus stations, stop car markers. I even think it helps to get a passengers prospective on things too.
I hope this helps, all the other advice given from other posters is top notch!