I see people post spoilers but block it out with a Spoiler-tag-button of some sort. How do I do that? Tried doing a search and tried using help and cant find the answer.

type "[.spoiler] -text- [./spoiler]" without the periods

Or, if you use the "Full Editor" instead of quick post, theres a drop down box in the top left that says "other styles". Spoiler is under that