yes, there are bottles that have the ratios on the bottle. i don't know where others get theirs, but i know the volume detailer supply houses have them, and some of the online plastics resellers have them available - 32oz carafe spray bottles with dilution ratios.
for me, i simply take the total size of the bottle, and divide by the total number of parts you have. if it is 32oz and you need to reach 7:1, divide by 8. that will give you 4oz, 8 times, to make 32oz. so, pour 4oz of water (i use a glass measuring cup) and then top off with product, or if you want to be extra precise, measure out 28oz of product to top off.
if you are a volume person and it is a product you will use a lot, or you want to make life easier even if you are not a volume person, and you bought a gallon of it, make pre-mixes in empty screw top milk containers or left over detailing product concentrate containers. i don't know about using milk containers with wheel brightener, lol, but, for instance, with megs glass cleaner, i will make 5 or so gallons of pre-mix out of the gallon, and leave the rest of the concentrate for later since it wouldnt be practical to have 11 gallon containers of mixed glass cleaner around. but it does make life easier to have several available so when i run out of glass cleaner in my spray bottle i can just fill 'er up with one of the gallons.