as we were saying a while back on the first page, a coching bantam would be the best to use if you could find one. But in your case with what you have, a houdan would be the way to go. You'll just have a lot more type correction to get back to silkie. Mottling is recessive so it will take 2 crosses to get the mottled pattern back. You could use black, white or blue with no problem, or even splash.
aside from the blues and splash, all would be black split to mottled, the blues would be half black and half blue split to mottled and the splash would be all blue split to mottled ( I think a blue mottled would look very nice in them is why I added that)
Once you make the first cross, you will have the benifit of the crest , beard, and 5 toes from the houdans so that shouldnt be an issue.
These will be 1/2 fibro melanistic too, so on your back cross ( the crossing together of the new chicks)
you will need to select for mottling and skin color, as well as feather type
Pick the best mottled pattern, darkest skin, and silkiest feathering.
Now you have to start all over and go back to silkie again.
Repeat the entire process outlined above and keep going til you get a nice true silkie back out of them. Being so many recessive crosses and genes to work with this will most likely take you an easy 8 years to get.
This is because you have that chick crossing year. In this year you dont get any better type really, you are just getting back the recessive genes in the mottling and skin color.
Would be a big plus to use bantam houdans if you have them, with standards you'll be fighting size too. It's not too bad, but would be just one more thing to have to cull for in the begining. Also start with nearly perfect mottling in the houdans. If you start with a patchy white bird which so many houdans are, it's going to be that much harder to get a good over all color on the silkies.