I often lift my left elbow, using the shoulder to move my hand up & down the neck. At the same time I try to move my elbow forward, to keep my lower arm as upright as possilbe. All of this without forcing anything of course. Thus the angle of lower arm - wrist - hand stays the same. I find it very confortable. Yet I see many players who let their elbow rest against their side and move their lower arm from there. So I would like to know what you guys do and what you think of it.
A lot depends on what feels comfortable to you, but keeping the shoulder still and moving from the elbow from the angle you describe is definitely doing it the hard way as it restricts movement. Bass necks are already hard enough to get around, without imposing extra restrictions. Having said that, going to the other extreme and going through contortions just to keep the optimum forearm angle causes problems as well. Bottom line - sounds like you're doing fine.