@Mark_Fuller that sounds like a great way to do the smoothing of the holes!
Is anyone doing the abrasive flow machining on their nozzles? We might be able to use water with rust in it as an alternative to the silly putty with oil and abrasive.
Does anyone do an acid bath?
@NathanielStenzel yepp sorry I mean the channel or nozzle hole
And if you make the hole before polishing the polishing paste gets inside your hole.
And in such small holes it’s really hard to get them out.
If your really want to get such small channel electroplated.
You can’t do it the normal way.
Their is now way to put a wire in our small nozzle channel and plate this way.
But you can do it with a chemical hard nickel bath as example.
But you would need to push electrolyte continually though it.
But it would add high costs 
So it’s easier to make it fully and add the hole later.
And next if we look to the resistance the channel produce on the plastic flow, we should first maybe look to the formula to calculate it.
This flow resistance depends on a few factors.
Channel diameter and lenght.
His smoothness. And viscosity of our fluid.
But if we look to this formula you would see the main influence comes from viscosity diameter and lenght.
Smoothness comes only in play if you channel is really long.
And in our case we have two channel.
The “heating chamber” and the nozzle channel.
And I think the part with biggest influence would be the nozzle channel.
@Zeno_Le_Hericy_Z-Inv yes in theory it would be great for abrasive filaments.
But one problem is nitride coating needs to be in the nozzle channel.
And that’s a problem to get in 