Yes. You do not necessarily need an expensive bulb intervalometer.

A simple intervalometer can help, and a common guideline is to expose each frame for about half of the interval between shots to keep motion looking smooth.

For the exposure transition itself, one practical approach is to shoot RAW and make controlled manual changes during the sequence rather than relying on per-shot auto-exposure, which can cause flicker. One answer suggests using a fully manual lens—ideally one with a smooth aperture ring, such as a cinema-style lens—so you can gradually adjust aperture in small increments as the light changes. Shooting RAW also gives you some room for minor exposure correction afterward.

So, based on the answers provided: avoid full auto-exposure if you want the smoothest result, use an intervalometer for consistent timing, and if possible make gradual manual exposure adjustments with a lens that allows smooth aperture changes. Post-processing can then be used for fine corrections.