There is no one correct method of using an adjustable but this is what I found worked when trying to find what settings work best...
Find the ONE setting that will give you an acceptable shave (DFS) with a couple of passes WTG and XTG.
If you want something CLOSER "dial around that" setting, for example if I can get a DFS from a 2 pass shave with my Fatboy on 5 and I want something closer then set it on 4 then 6. The "mowing grass principle" applies for the first two or three passes in other words use a less aggressive setting to start.
If you have some difficult areas there are a two approaches you can use, the safest method is to dial the razor right down and "blade buff" that area. The less aggressive setting should enable you to work around that area with less irritation and less concern for the correct blade angle.
You can of course dial up and buff but personally if you can handle a razor on an aggressive setting in a difficult area you might as well complete a whole pass on that setting.
Which really leads me to the last option, if you are feeling confident crank it up , larger blade gap, exposure and a sharp blade should deal with most problem areas.
WARNING: The Gillette adjustable's are mild compared to the Merkur's, just because you can adjust doesn't always mean you should, sometimes a DFS on one setting is good enough.