It appears that the way of the future is for buildings that make buffs require multiple building slots to become really effective (Snack Stand and Smokehouse so far, who knows what others are in the pipeline?)
Unfortunately, the times taken to produce the buffs are rather long, to say the least. It would be really useful if we were able to buff these buildings.
However, the mechanics of them makes it a bit tricky. If you have 2 snack stands, do you need two buffs to have the same effect as a single buff on a single building? Would buffing just one have a reduced effect?
I suggest a new zone buff: the Chocolate Fountain which has the effect of boosting the production of these buildings by the equivalent of one extra building for a period of time. If you had one Snack Stand, for the duration of the zone buff the production rates would be as if you had two; if you already have two in operation, then production is boosted to the level of three, and so on. This would continue the theme of diminishing returns from extra buildings that is inherent in their design.
As for how to get the zone buff? Well, there are a number of options. A recipe for the RPH is one, or it could be made available in one of the Excelsior sections like the various guide buffs.