Not all systems are the same in all the different stores. And, the CSMs at your store might have different rules than other stores.
Learn at your store. Ask for more training if you need to. Ask fellow cashiers and CSMs your questions. Take your time to learn correctly how to do those processes. Speed will follow once you learn to do everything right.
When I started as a cashier I always got the new sale ad and wrote the produce code on the pictures of the fruits and veggies in the ad. We usually sell more of those when they are on sale and it helped me learn them quicker than memorizing them.
I'm still a fairly new cashier at Kroger and still in the process of learning the ropes. It's very easy to pick up. It took me a while to memorize the PLU's, but I memorized most of them because I see them come through my line so much. At my store, WIC is considered EBT so we have to press the EBT button when a customer uses WIC. Every store is different. Ask for more training and you'll get it. They want you to be comfortable just as much as you do. I'm getting the hang of it, but I still ask questions if I don't know something. When it comes to learning something new, there's never a stupid question. Always ask if you're not sure of something.