There's some machining involved so its almost on topic.

I've got a job on that needs to have about 100cc +/- 1cc of epoxy resin mix
poured into an assembly as a filler to make it up to the required weight.
The assembly has an open top 4" in diameter into which the resin can be
poured. The resin type, amount and housing design are all non-negotiable as
they are defined by the customer. Pot life IIRC is 20 minutes or so.

I've got a couple of hundred of these to do and figured someone here has
probably done something similar. Any clues on a tidy way to do it so I don't
end up with epoxy everywhere but where it's meant to be!

I'm thinking batches of 20 or so using cheap throw-away plastic jugs to mix
the resin in and then pour it into the housings while they sit on some
weighing scales. Any advice or suggestions on a cleaner or tidier approach?

Thanks