WAIT!! I guess I saw a different (better for me) diy.
I DID NOT remove the bumper. This was much easier, if a bit riskier...
I (1) opened the hood an reached down through the kidneys to ID where the 10-12 attachment points are on the mesh insert.
(2) pushed from the front at each attachment point until the mesh and surrounding frame were separate from the bumper.
(3) then I slid the mesh as far as possible towards the driver's side of the car.
(4) --here's the delicate part-- I then twisted and pulled the mesh grill out through the hole it sits behind. I imagine a warm temperature helped, and I was careful to avoid scratching the bumper paint on the tight spots.
I cleaned it, let it dry, sprayed it and fit to back in the way it came out.
The clips were reachable through the kidneys again. Be careful if you try this to
(a) be gentle pushing on the relatively weak plastic mesh,
(b) twisting and extracting / reinserting the mesh, and
(c) aligning the clips before pushing your repainted mesh grill back into place.
Best of luck-