I know my beard map really well and unless there's some failing with the blade being sorely lacking, a single pass with the grain shave delivering clean and smooth (enough) is something I do most days. I'll only press on to a second pass with/across the grain for asbolute smoothness if I'm really enjoying the shave ... or the blade is lacking and it needs the second pass.
I'd echo
@Zorro above and say it's all in the prep. Less is more. Just a simple face wash with bar soap, hot water on the face while you build up a lather and take a minute or two to fit the lather to your face. Slow and steady.
Personally, I don't think the razor matters as I can use to super-mild Star Tech clone or the Wilkie Sticky ... or I could use a yawning blade gap razor like the R41 or the Yaqi SE (with a half blade). Slants, I do think have a minor effect on efficiency. It's the blade that matters and pretty much any that are not on the empirically dull side and those of the empirically sharp side are best suited to regular and milder razors. Aggressive gaps just open the door to in-shave tragedy.
Pop a Gillette Nacet Super Stainless into a Tech and I'll guarentee a better shave in one pass that any adjustable on 10 with an Astra Platium.