Regarding the process: for law review (and I'm using the generic term here), you need to do 42.5 hours of work per semester to get credit (1 credit per semester), so that averages to 3 hours a week. But it's independent work: so, depending on your schedule, midterms, etc., you could do 1 hour one week, 0 hours the next week, and 8 hours the next week. People who are writing that semester hit the 42.5 hour mark (and honestly, exceed it), and those who are not writing sometimes have trouble hitting the 42.5 hour mark, because we don't give you a million editing assignments.
In terms of what being on law review entails besides the writing, it's just independent work editing an article that you do on your own time. What we do is assign you pages of an article to edit, the type of editing you're doing (textual edits, source-checking, and/or Bluebooking), and an assignment due date. It is also possible to do most of the edits on your computer and you'd only need to come into the law review office for source-checking (which I will explain later), but still on your time.
For your law review article (what I keep referring to as "writing"), you write a 25 page paper for scholarly writing credit during your first semester on law review, to be submitted for publication consideration in our journals. The cool part about writing your law review article is that you can write about whatever you want, you get to pick your faculty adviser, and your scholarly writing doesn't get graded (just credit/no credit), so it's much less pressure than if you were doing a scholarly writing in a class for a grade on a topic that your professor picked for you. To be honest, writing your article is quite time consuming, but it's mostly on your own time (though there are deadlines built in so you can't totally write all 25 pages on December 1 at midnight). Plus, those who are writing get less than half of the editing assignments of everyone else on law review, that way everyone is putting in around the same amount of hours into law review. I think that self-pacing atmosphere about most law review stuff is what makes it manageable with whatever workload you have.