All of what has been said i've come across on various accounts as well.

It's mostly a combination of knowing your area of operations, getting vectored by ground control and using an automatic direction finder instrument, if your aircraft was equipped with one, tuned to a beacon nearby the airfield (or on the airfield itself).

In extreme cases an aircraft with better instrumentation could be dispatched, if one was available, to guide the others in. I've flown such a mission in a user made campaign for IL2:1946 that was based on Heinz Knocke's book.
The mission builder took a chapter from the book and adapted it into a mission where the player (in the role of Knocke) and his flight are flying alongside a Bf1110 on a relocation flight to another base, the reason being that the 110 has better instruments and could guide them.

Some examples i can think of that are probably reproducible in flight sims:

If a beacon was located on the airfield, the pilot could simply fly to it. He would know he was directly over it when the bearing needle in the instrument reversed (at the moment of overflying it). If the beacon was not on the airfield but nearby, the pilot could calculate a suitable bearing from beacon to home field and the time to fly for his current speed (aka compass and stopwatch flying).

Then, with knowledge of local terrain he could pick out a route to extend to and line up for approach, depending on ground control instructions, which runway was active and so on.

For example, in case of low cloud cover or haze/mist with hilly terrain on one side of the airfield, the pilot would overfly the airfield and then turn to a bearing that allowed him to descend safely and break through the cloud cover. Then he could turn back to the airfield (guided by the beacon) and make a visual approach. Or, in case of calm wind conditions, he could request an alternative runway, one whose approach path is lined up with lower terrain.

Mind you, radios back then were bulky (transistor-based electronics hadn't been invented yet) and only twin-engined aircraft and above had tunable radios.

Fighters had their radios pre-tuned by the ground crew and the pilot would then choose one of five available frequencies by pushing buttons in the cockpit: it's the sequence of red buttons on the top left of the cockpit panel in the Spits. I don't know if it's there in our CoD Spits because i usually fly blue or blenheims, but you can clearly see it in the IL2:1946 Spits.

Each of these buttons corresponded to one of the pre-tuned frequencies. Four of those were for voice communications and the fifth was usually tuned to a beacon. The trick here was that because the instrument panel didn't usually have an ADF instrument, tuning the radio to the beacon gave the pilot audio cues.

So for example, if you need to turn right to reach the beacon you hear dashes, if you need to turn left you hear dots (morse code) and if you're on the right course you probably hear a continuous tone (dots and dashes overlapping in sequence).

As you can see, it is very possible to navigate this way but it's quite cumbersome. Tuning into the nav radio deprives the pilot of communication with his flight and vice versa. Add to that the inflexibility of specific approach conditions (eg, sometimes you might not have the choice of a better approach due to wind conditions and you are forced to take the approach that is lined by a row of hills on either side) and it's easy to see that things can get dangerous.

Of course this is all for single engined fighters. Multi-seaters and twins could do a lot a better in that regard and as the war progressed they were fitted with increasingly better navigation equipment.