You're doing the right thing by using the step change to model the transient behaviour.
If ringing at the transition point is a problem, I've found it helpful to make the first C of a CLC section a significantly lower value than the second C. This has the advantage of presenting a greater damping from the load on what effectively has become a tuned circuit.
The nice thing is you can try some values and check out the effect without having to assemble the components.
Regards,
Duncan
