Opinions vary widely. I just cycled both of my tanks with RS reef mature last quarter.
I personally turned the skimmer on from the get go but just opened the drain to let it all flow back into the sump. I believe RS wants the skimmer running primarily due to the use of NoPox which for the most part I did not use as I started with dry rock and no lights. I still ran the skimmer as it needs to develop a biofilm to work right. If you have some live rock and running the lights from the start then you may want the NoPox. In the end I used a small amount but not much.
ReefMat. I did not install any media until about day 10-14 when the cycle was close to done or should I say just before starting to add critters