That's exactly what I needed to know. I did read the one line on the wiki, but was unclear if I could use the same type and stack them or just use multiple types at the same time.
I find myself with five 6-Hour Supply Rush kits after the Fall Event so I'd like to double dip my city. Activate as many boosts as possible (Tavern and Bottle), collect from my city, reset everything to a 24 hour cycle, apply a Mass Motivation Kit, then four 6 Hour Supply Rush kits and collect again. Since it's only supply buildings, the thing I'm always lowest of, I'd like to maximize the effects of the double-dip by burning up some of the many supply boost bottles in my inventory.
I'll spend the extra supplies on extra UBQs and turn them into goods, medals, and FPs. It's the best way I can think of to use those 6-Hours Rush kits up without messing up my 24 hour cycle.
Too bad the 6-hour rushes don't work on Terrace Farms and other special production buildings.