Fil Paulo Balat, Jefferson Eco, and James Macasaet wrote a blog post about output filter design to mitigate output inrush:
Switching converters on applications demanding reduced output noise may encounter delayed startup, or may not startup at all, due to excessive output inrush. Output inrush current, attributed to inappropriate design of output filters and its impact, can be minimized by increasing the soft start time, increasing the switching frequency, or decreasing the output capacitance. In this article, practical design considerations toward preventing start-up issues due to excessive output inrush will be presented.
See the full post on Analog Dialogue