Thanks that was helpful! I do understand recessive/dominant and I knew that the mottled gene was recessive. I was planning on doing silkie x mille fleur, then offspring x silkie and offspring x offspring. Then I would do (offspring x silkie) x (offspring x offspring). Would that produce some with mille fleur coloring with silkie feathering in that batch? (I know each chick would probably be a little different) Or would I end up with genetic monsters at that point?
 
		 
It gets a little complicated when you're dealing with more than just 2 or 3 traits. You get stuff like 81-box Punnett squares or even worse, 256-box squares!
If you order from MPC, you probably won't be able to get mottled Silkies. You won't see mottling in the progeny unless you use a mottled Silkie.
For some of the other traits ----
Feathering:
D'Uccle - probably H/H unless there is a bit of Silkie mixed in - normal feathers
Silkie - h/h - floof
F1's - Offspring will have normal feathers. - all of them will be H/h
F2's -
 If you want totally cute, I would recommend mating the offspring back to the Silkies. That way, you can get 50% of the F2's with silkied feathers. If you just bred the offspring to each other, you would only get 25% with silkied feathers. 
Vulture Hocks (from the D'Uccles):
D'Uccle - v/v - has vulture hocks
Silkie - V/V or V/v - no vulture hocks
Breeders generally try to eliminate vulture hocks in Silkies, so the Silkies are most likely to be V/V.  Although with MPC or any other hatchery, who knows?
F1's - there should be no vulture hocks visible in the F1's, as long as the Silkie is homozygous for no-vulture hocks.
F2's - 
This is another case where I would recommend mating the offspring back to the Silkies. If the Silkie is homozygous no-vulture hocks (V/V), and you mate it to the offspring which are heterozygotes V/v, you will get 50% V/V and 50% heterozygotes V/v. You shouldn't see vulture hocks. They are a recessive gene from the D'Uccle which you probably don't really want in the offspring unless you think they're really cute or something.
Mottled:
D'Uccle - mo/mo - mottled
Silkie - Mo/Mo or Mo/mo - not mottled
Offspring if the Silkie is heterozygous for mottling which is Mo/mo:
25% Mo/Mo - 50% Mo/mo - 25% mo/mo -
If the Silkie is homozygous (2 copies) non-mottled, you won't get any mottled F1's.
Leg Feathering:
D'Uccle - Pti/Pti or Pti/pti
Silkie - Pti/Pti or Pti/pti
The F1's will either all be wearing pants! (Pti is ptilopody, and it's usually dominant), or if the Silkie and D'Uccle are both heterozygotes, 75% will be feather-footers and 25% clean-legged. 
The F2's should mostly be wearing pants as well, but you would need to give away any clean-legged offspring that result.