You can use the same paint that Ford used to paint the body. There is no difference in the paint, but there are some primers for painting on plastic that promote adhesion of the top coats.
There are plasticisers that can be added to the color coat and clear coat to add some flexibility to the paint incase someone parks using the braile method, however the bumpers are still likely to get damaged and need to be replaced anyway.
I once got a $310 quote from a local body shop to paint the bumbers and side cladding to match the body color. Then 2 days later the renigged claiming they forgot a bunch of stuff and their new quote jumpted to over $700.
...Rich