Good finishing filler for fibreglass

[Yertis]

I'm fitting an after-market set of column switches to my TR, and part of that involves a new housing. This is in two parts, upper and lower. Like everything from this particular supplier they are strong and well made. However, asa designer, I'm a fuss-pot when it comes to how things look and I want to tidy up the profile in various ways, most particularly around the join lines. I want it to look as OEM as possible.

But I've never worked with GRP before, and need a bit of advice please. I've done a bit of googling around 'good fibreglass fillers' but the answers are a bit vague and generally to do with fixing the hole in your yacht. I want some stuff which can be mixed up in small quantities, bond well with the GRP and ABS (that I'm using for reinforcement), withstand temperature changes e.g. heat on hot day (it will be painted black) and be easy to sand and smooth. And take paint well obviously.

[gretsch-drummer]

If you're after an easy sanding, finishing filler then UPOL Dolphin glaze is a cracking filler. It's spreads really nice and self levels to an extent.

https://www.ebay.co.uk/itm/U-POL-DOLPHIN-GLAZE-440...