Best Epoxy/ Epoxy Filler

As per the title guys, making a ius forend the shottie. Got it all worked out but just need a good bonding agent for abs and metal, and some filler that is sandable

I use bog standard own brand epoxy from wilkinson's , a good filler is plummers putty it's a two part epoxy based clay like product that sets rock hard , it's exactly the same as mil putty only half the price ! Get it from B&Q/home base /wilkinson were ever .

Many thanks good sir, will have a trip to the nearest diy shop then.