My son and I shoot at a local 400 yard range as much as possible. This is what has worked for us.
I bring both the large (around 12" Dirty Bird) and the smaller (around 8" Dirty Bird) targets. Two of my rifles are always zeroed at 400, so windage is what we adjust for. I put up 4 tagets. One of the larger targets and 3 of the smaller ones. One of us takes a shot while the other watches through the spotting scope. If the wind is minimal, it will typically be right on target, give or take a min. From there, I just dial the wind and move onto the smaller targets. You should be able to see a .30 cals no problem through a decent spotting scope and even .223 if there is not a ton of mirage.
If the wind is bad, we watch for a splash in the berm behind and make an adjustment either way. Two - three shots and you should be able to dial the wind and be on center even in a fair amount of wind.
Lastly, this is assuming good ammo is used and a pretty accurate rifle. At 400 yards, the difference between good ammo and average ammo becomes noticable.