Organization is key to efficiency in any business. I would argue that it's even more important in detailing since a lack of organization can result in cross contamination. In a best case scenario, the oversight will require unbudgeted time to correct the mistake, thus costing money. Worse, it can cause permanent damage.
However, it's not always possible to go out any buy every brush organizer and pad holder available to store things separately. While working toward every item having it's own designated home, one affordable and important item is the bucket label. We can debate the merits of the 2-bucket method or another technique, but at the end of the day I don't want wheel chemicals or residue where they don't belong. Labeling detailing buckets is a good idea even if they're not all used every time.
I realized that I did an unofficial comparison of labels over the past couple of years. I ordered a set of the CARPRO stickers for detailing buckets. Many of their products are what I use for detailing. In fact, the CARPRO logo is even painted on the wall of our Evocative garage. Spoiler alert, I'm giving them praise now because one particular little thing turned out to be terrible, but I give real reviews.

The second set of labels used on our detailing buckets were cheap-o individually selected stickers from Detailed Image. I'd like to say that my astute business sense made me purchase these as a back-up. Truth be told, I need to add a few bucks to the bill to generate free shipping and figured these could sit in a drawer until needed, but I didn't think that would be the following week.
CARPRO Bucket Stickers

Detailed Image Bucket Stickers

Just in case you think there's some trickery going on, here's a 360-ish video of the comparison bucket.
Get labels for your detailing buckets and maybe even some back-ups. The blue ones are currently on clearance for under $1 each at Detailed Image. Click the link and you may be able to still take advantage before the price returns to normal. Even at a whopping $3-ish dollars, use them. Organization is key to efficiency, which leads to profitability, while still giving your customers a great value while providing service.