We use old fashioned "crane operator hand signals" where I hold up a hand where she can see it easily. Speed is usually always idle... Just put engine in and out of gear.
Pointing 'up" and circling the hand = forward. Clenched fist = stop. Point hand/palm down = reverse. And pointing port or starboard, steer appropriately. Increasing the hand movement quickly means = do this with a bit more vigor.
You’ve already got most of the good advice from the first few responses.
With respect to skippers and crew yelling back and forth to each other over the wind noise, FO nailed it. Our hand signals are slightly different, but agreeing on them beforehand is the key. For us a closed fist means “neutral”, as I will determine when to put into neutral depending on our way and the wind. We have one more signal that many won’t have: pointing port or starboard and spinning the finger to indicate “bow thruster” port or stbd if we need to kick it over just a little to keep the bow into the wind without adding way. Rarely used, but good to have at your disposal.
As already mentioned, Calculating scope based on the distance from the bow roller to the sea bottom is key, and a common mistake is using only the water depth. And it’s not rocket science. The scope references are guidelines. If in doubt, add a little more.
Regarding marking your chain, we have used various methods including painting links, or using zip ties. When we bout our boat 17 years ago, it was marked in fathoms. I don’t think in fathoms, and it made for too frequent of marks. When we refreshed our marks, we just did 25’ increments. We rarely have less than 50’ of chain out (in 9-12’ of water) and the next 25 foot mark is easily visible as it comes out on deck, so you can decide how much more you want in the water. Three marked links is 75’.
One other thing: if the bottom is shale, anchor somewhere else. It doesn’t matter how much scope you have - the anchor won’t hold in shale.