Scrub tack clean and condition. I also like to pack extra random parts just incase something goes wrong.
Clip ears, legs/feathers, whiskers, etc.
Shampoo thoroughly with whitening shampoo (White horse problems…) then put show sheen on top (of course avoiding the saddle area)
Pull/trim mane about a week in advance.
Depending on how long it has been, I bang my horse's tail.
Then I throw a scrim or fly sheet on him and make sure his stall is clean.
Oh, and I also make sure I have a lot of spot remover… Again… white horse problems.
Day before the actual show starts (not schooling) I bathe really well and use quicksilver on the socks and this special face shampoo I have on his face. I spray a shine spray (I use a mixture of the moisturizer pink stuff and vetrolin shine) all over excluding the saddle area and girth. On the saddle and girth area I just use moisturizer. Then I spray e-3 detangler on the bottom of his tail and brush out. Then e-3 fly spray all over and hoof oil (also e-3). No I'm not an e-3 advertiser i just love those products. I wait until he's dry and put a scrim on him before he goes in his stall. I also spray a lot of show sheen on his white socks so they don't pick up stains and dirt.
As for tack, the day before I do a good over cleaning. I dishwasher the bit if possible or just soak it in hot water and scrub it with a tooth brush. I clean the bridle down with leather therapy wash and condition with their conditioner and restorer but I use effax leder basalm on the reins. Then I do the same with the martingale and saddle. I soak my stirrup irons in hot water then scrub with a hoof pick brush to get the dirt out of the pads. Leather girth gets same treatment. During the show, I'll use a damp sponge to wipe down the tack and if it needs it I'll use leather therapy wash or effax ledercombi and condition with effax if needed. I wipe the bit down after every ride with a mint or apple flavor bit wipe. If you want anymore little tips, pm me! I love giving grooming and such advice.
Not sure if this is what you are asking, but my trainer rides him a few times during the week leading up to the show (on the days I am working). I make sure to do a brief trail ride during that week and the day before he leaves, hack him lightly (as long as he is responsive to what I am asking) and then walk him through the fields to let his mind relax and to be happy. I like knowing he can relax and have a bit of enjoyment before the trailering, tents and long hours that inevitably follow.