painting the bumper cover/ other car parts

[cesturdy]

bumper cover came primed. my plan is to use spray cans, and cannot wait as weather will be soon turning cold. i could only find locally a black trim & bumper paint by durocolor that can be used on plastic. The store advisor suggested that i do not need a clear coat for this paint as it already includes a finish, and that a clear coat from a spray-can may not have the flex-additive to take to plastic. Also like your opinion: my car is nautilus metallic blue. Would a black bumper be ok since the rest of the car is dark blue? would the contrast be ok? Since it is an old car (2007) i did not want to pay for an expensive paint job. Will also need to do something about the clear coat peeling off the hood and roof of the car? Do i remove all the clear coat and just reapply the clear coat, or do i need to add paint over the existing, or am i to sand down to the primer before adding paint?