Try to clean your bowl with a spatula before using the saran wrap and cover your bowl with a damp cloth. This might help to prevent crusting.
I usually prepare and keep my icing (very thick, “Julia’s glue” consistency) in one bowl though. Then I color the amount needed, thin it down to the consistency I need and load into the bag. See @Julia M. Usher ’s video here: https://m.youtube.com/watch?v=GO0_aNbL6Do (This is lesson 5, I suggest you to watch the whole serie.)
I am used to outline my cookies with a consistency different from flooding and I use a PME #1 tip. I always use white royal icing, no matter the color of the icing I am going to use for flooding. The color of the flooding will bleed into the thin white outline (the damn), and I also learned to hide the outline by covering it with flooding icing. So this cuts the bags for the outlining consistency to 1. I also use this same consistency and color for piping borders or lines or little dots. Some people use the same consistency for outlining and flooding though, and tipless bags, so they don’t even have this one bag to prepare.
At the beginning of my cookie journey I was preparing each outline consistency matching the flooding consistency!
I don’t make so many cookies, just those for my monthly tutorials here on Cookie Connection and maybe another project a month. But I have learned to plan step by step everything. Having a good plan about the design and the colors you are going to use helps to be efficient. And also working on more projects at the same time helps to maximize the use of royal icing.
The only one time I had to prepare a lot of colors was recently for this set wet on wet below: 8 colors and 9 bags just for one wet-on-wet cookie (the white outline and white flooding consistencies are missing in the picture)! But It has been so much fun.
I don’t know if I have been of any help. You said that you are at the beginning of your cookie journey but I can tell you that little by little while you practice and gain experience this tedious process will get easier and you will find what will work better for you.