One thing I will suggest,be careful about the first brass you size after cleaning your dies.Lube them well! And you do not want residual solvent ,etc confusing your case lube.
For some reason WD-40 is a passionate topic here.We have had many discussions about it.The inventor was trying to make a Water Displacing preservative.One of the first applications was the workings of Atlas Missiles.
The inventor tried to be secretive with his formula. MSDS laws pretty much got past that.Someplace ,researching for a WD-40 discussion here at TFL,I found the alleged ingredients. Primarily Varsol,an industrial petroleum distillate solvent,and hydrogenated heavy mineral oil.
They hydrogenate vegetable oil to make Crisco. Peanut butter oil gets hydrogenated.That makes the stiff grease texture.
So,not quite a perfect descriptin,but if you fluff and puff a no-additive gear oil to a grease like merengue or mayonnaise(or Vaseline),then dissolve it in parts washing solvent,its pretty close to WD-40.
If you degrease your dies with Brake cleaner,etc,I do suggest they need something for preservative.
Feel free to disagree,but IMO,WD-40 is fine.
I have not done this,but it might be that lanolin or RCBS case lube dissolved in mineral spirits or laquer thinner would penetrated a thin film of case lube over the die.IMO,that would work for me.
I'm not quite comfortable with the alcohol carrier in spray case lube for an anti-rusting application.