The Prado's web site says mornings are busier and recommends afternoons (starting at 14:00). Google's Popular Times function says opening is less busy, then it gets busier until noon, then less busy until 15:00 then busier towards closing. https://i.imgur.com/DrMvZIx.jpg I usually trust Google on this, since I believe it actually tracks people who use its apps, but I wonder why the museum says something different.
If Google is correct, I'd go at opening, get lunch around noon when it gets busiest, then return. Does that make sense?
How would you recommend spending lots of time there and avoiding the busier times?
Having checked recently, tickets seem to be available on short notice. For example, there's availability tomorrow morning at every time other than the first time slot. Is that unusual?
Also, can you still re-enter? I've seen lots of posts that say you can, but they are not very current.