A couple of other points.
Take plenty of ammo. Its bugger all use sitting in your cabinet at home. It’s easy enough for a rifle to take a knock and you end using 10 rounds to get in back on zero. If you are culling hinds you may get several shots in the day. Whilst the vast majority go down on first shot, we have all had red deer that have taken three or four shots to go down. They were dead on first shot but no one gave them the message.
Take a couple of boxes - 40 rounds. You will probably shoot five in the week and come home with 35. Most estates have a range and often a good opportunity to have some fun.
If you have two rifles and room in the car - take both, even if other is not totally suitable.
Zero rifle to shoot 4cm high at 100m. This means you don’t have to worry about range and adjustments and have a point and shoot to a bit over 200m. When its sleeting, range finders struggle. Cold fingers struggle on turrets. Just get into the beasts, get down, cross on kill zone, squeeze trigger, beast down.
Fitness - if you can a few days before you go do a couple of long hard walks in your boots. Stalking in the north of Scotland is pretty hard physically, especially if you are well out of shape.
But, stalkers up there have a special type of fitness / stamina that allows them to keep going all day long on a mars bar and a can of iron brew. Don’t even try to compete. Start slowly and start cold - don’t have too much clothing on. But do have a warm layer in your pack. Go at a pace where you can comfortably talk. Especially for the first hour. And hopefully he will be using glass, so that you have to stop and look long and hard. If he is using thermal he will scan quickly and move on - bad luck!!
Whisky - tradition is that a bottle is opened and cork goes in the fire. Again don’t try and compete. You will regret it. You will be out on the hill at 5am. However some don’t let a drop of the heathen brew pass their lips.
Gloves and socks. Have two pairs with you on the hill. Have a light pair for the walk in etc/ climb in, hard going crawling etc. these are the ones you get wet. Then have a warm dry pair in the pack. Put these on when sitting up, waiting and later on when cold and tired. Ditto with socks. A dry pair later on in the day when you are cold wet and miserable makes a huge difference even if your boots are damp.