I recall there was a mercy flight under similar circumstances that crashed into a mountain out near Cunninghams Gap west of BNE.
Lincolns had a radio compass as the only radio aid to navigation. They were also equipped with a military form of DME called Lucero. This was used at selected military bases only and there were no charts as it was nothing more than a homing device to get the aircraft an accurate overhead of the beacon and from there you were on your own. In the case of Ron Raymond's approach to Eagle Farm in his Lincoln, he would have to arrange own separation I suspect rather like present day OCTA. I don't recall if Brisbane had radar in those days.
En route navigation was usually by DR coupled with long range HF bearings and astro compass shots of the sun or stars. Hence navigators were part of the crew. In the case of the Mount Superbus crash of the SAR Lincoln you refer to, that flight Townsville to Eagle Farm Brisbane airport was flown totally at night and in cloud most of the way. One theory was the navigator may omitted to set the variation counter on his prime compass system judging by the 10 degrees track error all the way to Brisbane. I recall the variation was 10 degrees East.
It was virtually impossible to obtain accurate pin-points at night due cloud cover as well as sparse ground lights on the night of that accident. When the Lincoln reported the lights of Brisbane in sight and ATC cleared it to descend as required, in fact the lights were probably in the area of Oakey 50 miles off track. This would indicate that at the time of that particular accident Brisbane did not have ATC radar.