It is best to use a Master Sprinkler when planting to increase the size of the fruit and the chance of Rainbow and Gold since they are Growth Mutations.
It is the best sprinkler out of the Gear Shop sprinklers. Additionally, its lasting time is doubled, unlike the other Gear Shop sprinklers, it lasts for 10 Minutes.
Master sprinkler has an increased area of effect, making it even better than other sprinklers.
A common strategy to use a Master Sprinkler with is called the Sprinkler Method, which consists on using one sprinkler of each type to maximize plant size, growth speed and mutation chances. Comboing with special sprinklers, such as Berry Blusher Sprinkler, or pets with special abilities, such as Moon Cats, can also be a good option.