So you want to end up with birds that breed true for mottling, and for most Silkie traits (toes, crest, skin color, etc). Then the blue and chocolate colors and the silkie-type feathering can come in various combinations, but don't all have to be in the same birds.
Blue is incompletely dominant, so easy to track which birds have how many copies of it. Chocolate is sex-linked so easy to spot in the females, but recessive in the males. Being sex-linked, it can be relatively easy to track too. Mottling and silkie feathering are recessive, so they will be the harder ones to get right. Other Silkie traits like crest and 5th toe are dominant, so they are easier to recover by crossing back to Silkies if you need to.
I think that making mottled Silkies is the first logical step.
Because of what Silkie colors you already have, you can have blacks and blues at all stages of that project (you probably want to avoid making splashes when you need to be able to see if the bird has mottling or not.)
You could start with either the Mottled Pekins you have, or the Mottled Brahma you mentioned being able to get. You could even start a line from each, if you want.
Unfortunately, I think that method or something similar is probably the best you can do at one stage of the project. I've spent a while turning it around and around in my head, and I don't see many options to make it easier or faster.
It would work out to something like this:
Cross A, breed a mottled bird to a Silkie. If there is any variation among the chicks they produce, select ones with as many Silkie-type traits as possible. For example, you want a crest and 5 toes.
Cross B, breed males and females from Cross A to each other. About 1 in 4 chicks should show mottling, with about 1 in 16 showing both mottling and Silkie feathers. In this generation, be prepared to hatch as many as you can, and eat a lot of fried chicken. You might spend quite a long time at this stage, incubating as many eggs as you conveniently can, at every reasonable opportunity. Or you might lucky and get one correct chick in one of the early hatches.
Once you have mottled birds from Cross B or later crosses, you can go to a more efficient breeding plan:
repeat Cross A, breeding your mottled project birds to pure Silkies. Select the offspring with the best Silkie traits (preferably including silkie feathering).
Breed Cross A birds back to mottled project birds, to get 50% mottled chicks and 50% not-mottled. Select the best of the mottled ones (most Silkie-like), and repeat Cross A again with them (breeding back to pure Silkies.)
Even if you don't get a bird with both silkie feathering and mottling from the Cross B generation, I think if you pick a mottled one and continue crossing back to pure Silkies you will get the silkie feathering in time, probably not many generations away. And you did say you want at least some Satins as well.
Once you have birds that are mottled AND silkied, your back-crosses to Silkies will just need to focus on other Silkie traits and the mottling, because they will all be pure for silkie feathering.
At some point, likely within 4-6 generations, you will have a nice group of mottled birds that show many Silkie traits. Some or all of them will have Silkie feathering (depending on which ones you selected at which stages) and they should be pretty good for crests, 5th toes, comb type, hopefully for dark skin as well, and for general body type. They will include blacks and blues and maybe splashes.
For adding the other genes, do you know how the chocolate gene works?
You can track an alternating pattern of generations:
Crossing chocolate male to not-chocolate female gives chocolate daughters and sons that carry chocolate.
Crossing a male that carries chocolate with a not-chocolate hen will give some daughters that are chocolate and some that are not, with some sons carrying chocolate and some not. The chocolate daughters can be used to cross back to not-chocolate males again.
You can cross chocolate directly into your mottled/Silkie project birds, or you could cross a Chocolate Pekin to the Black Standard Cochin females and then use those sons or daughters with your mottled/Silkie project birds.
You can also cross mottled project birds directly with the Standard Cochin and then cross their chicks back to the mottled project birds, giving about 50% mottled offspring (hopefully bigger), but then you will have to do some re-selecting for other Silkie traits (feathering, crests, toes, comb, etc)
Likewise, you can cross to the mottled Brahma to add size, and you will not need to backcross to recover mottling. But again, you will have to re-select for other Silkie traits in the next few generations.
For most of this, it doesn't much matter which parent is which breed or color or has which trait. Chocolate is sex-linked, and the black skin of Silkies requires a sex-linked gene that allows dark skin. A Silkie rooster will give that gene to his daughters, but a light-skinned rooster will not. Half-Silkie sons will inherit one copy from their Silkie parent no matter which direction you do the cross. If you keep crossing back to Silkie, and selecting for the best Silkie traits, you will probably end up with the black skin at some point without having to pay careful attention to the genetics of it.
I am assuming you won't breed from any bird that is obviously unhealthy, so I haven't bothered to state that each time you need to select birds for breeding purposes.
