The CFP (Construction Foam Pack) was created so that you don't have to repeat that refilling proces for the CF Sprayer over and over. Combine the CFPack (and a CF Sprayer, of course) with some Scaffolds, and you can get yourself a creeper-proof bunker in no time!
The CFPack is able to hold up to 129 CF Pellets (258 sprays), and is recharged at a Canning Machine, saving your mouse and finger from excessive clicking. The CFPack itself goes in the lower slot (where empty Tin Cans would go) and the CF pellets go in the upper slot (where food would go).
Unlike when using the BatPack, using the CFPack won't recharge/refill the actual Sprayer tool, simply maintain its initial charge level. The CFPack must be equipped in the chest slot to function.
See: Crafting Guide