Been a long time since I painted a car.. and the last time I did, it was a fiat with chrome bumpers. I am hoping monday to have the body of my saab painted, but I still need to sand and prep the soft plastic covers for the bumpers.
I know I need a flex agent for the colour and clear coat.. but do I need it for the primer?
I defer to the greater knowledge on this board but I think you do, yes, unless you're using special plastic primer which should work OK without a flex agent.
Then again, I might be talking out of my backside 
If the primer doesn't stick to the bumper, nothing on top of it will will have a chance. Seems to me the primer is the most important part, and should have a flex agent, or be that special plastic primer.
Ironically, I've had 4 Saturns but never had to paint any plastic on any of them - and since their bodies are mostly plastic that's kind of amazing. 
I found both a flexible plastic primer and bumper paint in aerosol cans at Advance Auto which has held up so far without issues
When I painted my Miata I just wetsanded the bumpers and painted them with the same paint as the rest of the car, no flex additive. It has held up fine for the last four years.
Scuff up the bumpers (sanding them of course), clean them (alcohol, thinner, and/or wax cloth), and paint. If there is a decently smooth layer of paint, a primer isn't necessary. How smooth you want the paint is up to you as you can sand and clean between coats.
For urethane bumpers- a flexible paint, such as bumper paint (aka polyurethane) is necessary.
socalwrench wrote: Scuff up the bumpers (sanding them of course), clean them (alcohol, thinner, and/or wax cloth), and paint. If there is a decently smooth layer of paint, a primer isn't necessary. How smooth you want the paint is up to you as you can sand and clean between coats. For urethane bumpers- a flexible paint, such as bumper paint (aka polyurethane) is necessary.
A flex agent is not necessary. Modern urethane paints will flex just fine. I have a friend who is a chemist for PPG tell me that.
Adhesion promoter, epoxy primer, high fill primer, epoxy primer, base, clear
http://www.wmbarr.com/product.aspx?catid=1&prodid=72
We used this at our tech school body shop. Works well and is also a flex agent too.
I can tell you this. Whatever Earl Schieb uses does not flex. I backed into a post last week and my bumper paint cracked like glass.
What filler (If any) will do the trick? I can't imagine bondo cutting it.
kreb wrote: What filler (If any) will do the trick? I can't imagine bondo cutting it.
Evercoat 411 Poly Flex flexible glazing putty works great.
Oh and +1 on the Bulldog adhesion promoter !!
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