+1 for cleaning sunroof drains while you've got the rear bumper off.

 

I've removed the boot liners either side.. no bolts... help....

 

If you pour soapy (not sudsy) water down your sunroof drains (2 front, 2 back) and they drain out like they're supposed to, then you don't need to "Clean" them. If you use something too aggressive (like a coat hanger), you can rip a hole in any given drain and cause a real problem. Don't fix something that's not broken.