The effect you're trying to get is quite easy to do actually. Disassemble the watch and put just the dial and hands in the oven! Medium heat for awhile, just take them out whenever you're satisfied with the ageing effect. The dial is going to get flatter and duller and the lume is going from white to yellowish and finally starts to get brown, just stop when you're satisfied. You can also spray it with matt clearcoat, but be advised that that turns the lume even more yellow, so if you started with the oven treatment, you maybe want to finish that before you're satisfied, due to the combined effect. Been there, done that...
The reason for the clearcoat isn't in my opinion mostly for dulling the dial, it's more for getting an uneven surface on the dial which some old gen dials have but not all! Therefore my recommendation is go for the oven treatment only! Oh, and don't forget that the dial and hands may need different lenghts of exposure (the dial takes longer if the memory serves me correctly).
Good luck!