Replacing caulk around a tub when the gap width varies

I'm replacing failed caulk around a bathtub. The gap between tile and tub is narrow along one wall but wider near the corner, where the previous bead looked like a lumpy rope. I removed the loose old material and let the area dry. Would you use backer rod where the gap is wider and then one continuous silicone bead, or is there a better way to keep the finished joint neat and flexible?