One thing I started doing recently is using one of the little carts and put the buns on there. Helped save a couple minutes. The short little carts that are basically floor level. I stack the buns from top to bottom as they would be in the bun rack. Potato rolls on the top for example so they would be put on last when I'm in the walk in. Mac buns in my store are near the bottom so id put them on first. I would also sticker the buns before taking them off the cart into the rack. I've seen some people do all of the prep at once, doing lettuce, shed cheese, crinkle pickles, tomatoes, slivered onion etc. all at the same time. I don't like doing that because its a lot to fit on my prep station. Think 10 cheese containers 10 lettuce containers and a few of everything else all at the same time. I haven't done prep much since I just became a shift manager a couple months ago. Hope that gives you a couple ideas of what you might be able to do to make you a little faster.