Merc. Milan Bumper cover

I'm going to have to paint the rear bumper cover of wife's Mercury Milan and think it might be easier to take it off the car then paint it. I'm wondering what I will need to do to get the bumper cover off the car. Any help appreciated.

I had a body shop guy tell me to leave it on the car and just mask it off good so I figured I'd better do it that way.

I would say you can do it either way, and both have pros and cons. If you take the bumper cover off, you can focus more on getting the paint smooth and you won't have to worry about overspray. However, taking it off is a somewhat tricky operation. You have to be very delicate with it or the cover could bend or crack. If you leave it on, you won't have to worry so much about damaging the bumper cover, but you will have mask the surrounding area heavily and precisely, which can be a pretty tedious job.
Basically, are you better at handling fragile items without damaging them, or masking surrounding parts to protect them from overspray? Whichever you find easier is the way to go.

The bumper cover already has a bit of filler material in it and I did prime it the other day. I'm guessing it might be better to not move the bumper cover now. I have plenty of stuff to cover the rest of the car with, I'm kinda waiting for a low humidity day right now, we've had almost nonstop rain here and I imagine the humidity is quite high and I'm in no hurry..

Well now that you've mentioned the filler material, I'm going to recommend leaving the cover intact. It's tricky enough to remove a bumper cover without damaging it, but without the body filler chipping or flaking off? It's damn near impossible.
Masking tips; don't skimp on the tape, get the top of line stuff no matter how expensive it is. Cheap masking tape can easily ruin a paint job, trust me... I've leaned that the hard way.
However, you don't need to waste money on masking paper. I've found that old newspaper does the job just fine, just use multiple layers and check for gaps and tears before painting.

Thanks for the replies, I've been saving up a bit of newspaper so I'll be good there, I think I bought enough masking tape also. I used a bit of it for the priming I did but there should be enough for the job. I have an old car cover that I'm gonna use for the front part of the car, I've used it before, works pretty good for this.