Grizdango

For long range scanning / finding high amount ore nodes: Rope ladders and digging straight down let you get a prospector reading and back to moving in like 15 seconds, every hundred blocks or so is plenty if you're setting up a grid of results in an area. You only need to go closer if you're zeroing in on a specific ore you already have a high concentration of. Just dig until you hit rock, use prospector pick, dig 3 blocks down with pickaxe, second prospect, dig 3 more blocks, last prospect. Then rope ladder up and pull your rope ladders back when you're up top. Seal the hole or not, your choice. This long range grid you set up this way will be good for finding other ores in future too, not just the one you want right now. It's a one-off long term investment. For short range scanning / once you find a high yield area and want actual ore: Once you have a sufficiently high concentration, you pick a spot to dig to mantle. I advise having 2 full stacks of rope ladders here. Dig straight down and take a prospect reading (in short range mode) every 6 or 7 blocks. If you get ore detected with one of your prospect readings, great dig in directions to find it. Otherwise dig another 6/7 blocks down and keep prospecting. If you reach mantle without finding anything just climb straight up with your rope ladders and then pull your rope ladders out once you're topside. If you reached mantle without finding anything move 12 blocks in any direction and repeat. First hole should be the center of a square of prospect holes, just work around in a clockwise direction or whatever. If you're at very high / ultra high from your long range readings I've never had it take more than 3 vertical shafts to find a deposit of the ore I'm looking for. TL;DR Dig straight down and use rope ladders to go as fast as possible. If you mess around making staircases or avoid ladders it takes forever. Generally once you find a single deep deposit of an ore you're either set for life or at least good for the next few dozen hours.