I don't know that this is helpful to someone sizing in a traditional lube-sizer but it might be worth some experimentation. I am powder coating mine using the airsoft pellet electrostatic method. Mine end up near .405 after coating. I pass them through a Lee (dry) sizer at about .4015 or so and a little silicone spray lube makes a huge difference. I found that it was best if i shot some in a plastic container and then added the powder coated bullets after a few minutes, as the solvent with the silicone lube was quite volitile and melted the powdercoating just a bit. My only concern at this point is whether the silicone lube will leave the bullets slick enough to prevent a good grip on them when taper crimped. Sizing effort with the silicone lube and a polished Lee sizer was way below what it was without the silicone spray.
Paul