Having looked into this subject in detail, up to just after the Battle of Britain, most single pilot visual navigation was done using ground features. Pilots would tend to be quite "localised" and would develop a clear mental picture of their locale and be able to navigate using known features. Outside the known area, map navigation was done mostly by "map crawling". And this all seemed to work adequately until after the Battle of Britain when the fight became more offensive and it was now possible to take the fight to the enemy. Single seat fighters were now being used on low level offensive attacks in Europe (known as "rhubarbs" due to their very low level nature) and it was rapidly discovered that the navigation techniques used up to this point were not sufficient due to the lack of visual range at low level, particularly in the flat areas of Northern France, Belgium and the Netherlands which had very few features with vertical profile. Pilots were getting lost and aircraft were being lost.
The Air Ministry looked at ways of improving Navigation and part of the plan was to use (later Sir) Francis Chichester, who had considerable navigation success flying to Australia and New Zealand single handed to help develop these techniques. Chichester had been prevented flying on active service due to his eyesight and had already written several articles and books on Navigation, so was glad to help. He later flew with ETPS developing the techniques as a pilot without wings - which often caused consternation.
What they came up with was the "Clock/Map/Ground" technique which allowed accurate navigation while giving most of the available pilot capacity to looking out and flying accurately. The RAF were still using it in the 1980s when I trained and in the 1990s when I was teaching and it still forms the basis of Navigation learned by RAF pilots today.
A lot of this is covered in Chichester's Biography "The Lonely Sky and the Sea" which I thoroughly recommend.