Should I use a regular food warmer or one that is also a Cooker?
Would it warm up faster in the cooker warmer? Like in 5 minutes or less?
Is the bun already cooked? You can try microwaving the bun with a slightly moist paper towel over it to prevent dry and hard bread.
Yes store bought brand, but I am warming many of them up.
i think it depends on whether the buns are to be soft or crunchy. the microwave/wet paper towel method is great for freshening up soft ones but oven warming is the only way to get the crunchy ones heated and retain their crunch outers.