Preparation for fibre glass

[skotl]

I've got a flat bed cover for my pickup that (appears to be) made from fibreglass. It's doing a decent impression of some crazy paving and, as I'm putting it up for sale in a few weeks, I'm keen to see what I can do to improve it.

Would I just treat it as plastic, sand it smooth and spray with plastic primer? The original finish is black if that helps.

 

[Bobtail4x4]

if its that bad you need to grind out the cracks and use surface tissue, then fill,

 

[Maxakarudy]

Grind the cracks out as said, but at a shallow angle, then use P40 fibreglass filler, it's same as tissue, but more convenient, no need for filler if it's done right, just primer.