i got a new front bumper from honda(looks amazing!) and im painting my 88 crx si, the only thing i havent done before is spray primer on a raw plastic bumper. how should i got about doing so? im using epoxy primer, what grit should i scuff the bumper cover up with? and do i need any flexing agents in the primer? and how long should it sit before base/clear?

also, when bondoing curves in the body, should i sand up and down, or along the curve to get an even coat?

thanks in advance