I am sorry to give a useless reply but I think the answer is "it's hard".
That's why dead reckoning is not half as good as they make out when they teach it in the PPL (while slagging off GPS).
The #1 trick in dead reckoning navigation is picking ground features that are unique within a reasonably wide area. For example no use picking a lake as a waypoint when there is another one 2nm away, especially if the other one is even vaguely similar. (Picking the group of two adjacent lakes, with say the smaller one on the left, might be a better idea in this case). Same with towns & villages and that's hard because so many villages look exactly alike. It's easy along a coast which has plenty of curves and nicks in it; you just tick them off on the chart. Roads are hard to use; if using them one should pick up on a weird looking intersection which one isn't going to see every few miles. Railways are often hidden in vegetation and can't be verified unless one is on top of it by using a GPS first; it's said that the clue is the straight lines and gentle curves but plenty of hedges do that also.
The #2 trick is not to just fly for X minutes and then start looking for the expected ground feature. One should check off other (probably less obvious) features down below as one is progressing along the route. This is how you do street-level nav from a map in a car; you (or preferably a passenger) check off each street as you pass it. Obviously this jacks up the cockpit workload, but some people like it
That's why so many official VRPs are useless - except for the locals who can't possibly understand how anybody can fail to recognise them.
None of this stuff works on nice hazy English summer days
Specialised units (e.g. S&R helicopter pilots & the military) get specialised training and lots of currency, plus they tend to know the area. Plus they use a GPS whenever it's useful.