have read a lot about the scrubbing.. in short, this is what I hear and what I have followed. If you have a new tank that is going to cycle... try to pick off what you do not want on the rock and give it a slight scrub. You don't have to do this, but you might keep hair algea or something that you don't want out of your tank, that is going to bloom later.
You have to leave rock only in your new tank until your cycle is complete. Also, if you are putting a sand bed in, do it once you get your rock in place, that way it is more sturdy and cant be kocked over as easy.
I agree about spacing your rock out some more. I put one big chunk in, and then sorta angled them where I had 1-4 inch spaces between so my fishes inverts ect could feel more at home AND clean between them.
We have 125g and had all fake stuff at first, so just recently started adding the rock. I alredy knew the swim patterns and likes of my fish, starfish etc. So I tred to accomodate them. You can also super glue together what will not stay in place. However, I think you have more bigger than smaller pieces so for you this may not be an issue.