We were there last Tuesday, a day with the fountain show. We didn't get there as early as we had planned, really wanted some more sleep. So it was around 10:30 when we got there and the line was HUGE to get into the Chateau.
However, my husband spotted a sign with an arrow towards the gardens ( towards the back left when you are there looking at it) and found that there is a little booth back there where you buy tickets for the gardens/fountain show. He bought the tickets with no wait at all and summoned me from where I was waiting back in the big line while he figured all this out.
We walked right into the gardens, saw the fountains, walked back to the Trianon/Hamlet/etc. and spent a few hours doing all that. Then, by the time we were ready to go into the palace, there was no line at all to get in.
I believe this is the advice RS gives in his book for a later arrival, but it wasn't clear from the book or upon arrival that the big line wasn't necessary to get back to the garden and the staff were not much help either (they just told everyone to get into the big line).