This is a very short service that comes right after attesting to Clear. It consists of going out into the world and noticing a few things, in order, and repeating that process "until you feel bright."
No auditor is needed for this process; Scientologists do it themselves.
When it was introduced, there was a separate charge for this service (in 1982, it cost 165 pounds in Great Britain or 365 dollars in Australia) but recently the price has been included in the cost of the Clear Certainty Rundown.
The Sunshine Rundown is described in HCO BULLETIN OF 13 NOVEMBER 1981 and the instructions are given in HCO BULLETIN OF 16 NOVEMBER 1981.
What Is Scientology? describes this service as giving "extra shine" to the state of Clear. It says the service may take about a day, but it seems likely, given the instructions, that a few hours would suffice for most people.
This short action adds extra shine to the state of Clear. By doing it, the Clear is becoming self-determined in his new state.