When dealing with large gaps within a home, consider using backer rod as filler before caulking. Backer rod provides a flexible but yet firm surface to apply caulking to. Another benefit of backer rod is its ability to repel water and help seal off air leaks. It will also provide ideal joint design (two points of adhesion with less of the product applied in the middle of the joint) for caulking. Using backer rod will inevitably save you and your customers money, as it is less expensive then caulk. Next time, before you fill a gap with large amounts of caulk, consider backer rod.