Winds up higher are the bugaboo. It is not a guess, or an art. It is certainly science. The problem is that we don't have enough gear, time and money to measure the winds along the path of the bullets flight (yet). For that reason, we have to take the data and indicators we do have a make a best estimate of the affect on the flight of the bullet. With more time and data, those estimates get better. I used to look at wind forecasts and avoid going to the range on windy days. Now I only practice IN the wind.
The wind speed at the ground is technically zero, the grasses a little more, your face a little more, trees a little more. Some bullets will be 20 to 30 feet above the ground shooting over flat ground out to say 1000 yards. So most people use the wind at the shooter, 5 or so feet above the bore, and go from there. But don't be scared to try other things during data collection sessions at the range. Also, vary the location. You need to shoot facing into the wind, wind at your back, N, E, S, W, off cliffs, over flats, etc. to confirm the data your cards or ballistic solver give you.
The grass and face give you a hint, but will usually be a little low. Wind at the shooter is more important than wind at the target. Mirage will also give you good data. Watching other shooters impacts, and traces, is of course the best data you can get if the wind does not change.
A spotting scope with very good glass, right behind a shooter, on 10 to 12x will usually let you see trace. With mine, I see it probably 90% of the time. Understanding what the trace is telling you is also important. When the bullet is always left of the trace, the wind is blowing right, and vice versa. Sometimes I see a snake and then I just go with no wind correction.
Also, when wind is an issue (700+ yards) so is terrain. How the wind moves around a bluff, canyon, over water, dark foliage, etc. all has a small effect. When you get out to 1000ish, you have to start to account for aerodynamic jump due to the wind as well. This was, for me, the final piece of the puzzle to hitting 1 MOA targets out past 1000 yards.
Rapid fire strings in between gusts is a losers method...knowing what the wind does is what skilled shooters do. Control what you can, adapt to the wind. Most of the LR matches I shoot require 1st round hit on steel, a few a second round hit can score.