Some lines are really long, and some are not. If you plan on a picture down main street at MK, then you will wait in a long line. Here is my secret tip, so don't share it on these Boards with others, go to the bridge at the Hub to Liberty Square. Walk across the bridge. Immediately to your left there is a CM with photopass. He/she will take great castle shots and the line is generally way, way, way shorter than straight down Main Street.

Shhhh! Tell no one.
It only rained heavily one day that we went, and I don't recall seeing CMs for photopass during our downpour, but remember you do get pictures on attractions for free with DMM too.
I've never seen Photopass CMs at a resort. I've never been to a waterpark at WDW. There is a Photopass Studio at DS that has CMs to take photos? Bank on the CMs being at the big 4 parks.
My DW purchased the DMM package with our trip. I was a skeptic. I have printed two pictures for my office, and created a large vinyl artwork for our home and printed a third picture for our home in a 5 x 7 frame I bought at Emporium during our vacation. I'm no longer a skeptic. It was a great addition to our trip and I'm glad my DW purchased it. Again, shhhh!!! Don't tell my DW I said that.
If you use the
MDE app, there is a tab for photopass pictures and you can see the photos. I don't think the watermark over the pictures does it justice but our pictures turned out really well. I'm not sure if you can purchase DMM after-the-fact, as my DW was responsible for the purchase.