I just did this with my Silkie and some feed store chicks a month ago. My Silkie Violet is raising a Turken (Rue), an Appenzeller Spitzhauben (Clary), and a Lavender Orpington (Hyacinth). Here's how I go about it:
Make sure she's good and serious about being broody. I wait at least a week or two, and I leave fake eggs under her all that time.
Get a couple of chicks from a reputable source. I like getting chicks rather than hatching eggs because I already have a rooster; I need no more boys!
Wait until it's very dark. Sneak out to the coop and leave the lights off. It's best if mama-to-be stays sleepy.
Stick the babies under her backside one at a time. Listen carefully for the mama hen noises. I take the fake eggs out then because I guess I think my hens can count? Idk. Like, there were 3 eggs and now I have 3 chicks and there are still 3 eggs... hmmm....
If she starts to peck the chicks aggressively, take them out and try again the next night.
But if you hear those soft mama hen clucks and happy baby trills, then you just sit and listen a bit to make sure she doesn't reject them.
Go back out first thing (I go out again before dawn) and make sure they are still under her and happy. If they are huddled across the coop from mama, you'll need to take them out and try again later.
Keep checking on them periodically to make sure they are bonded, but be prepared to raise them in a brooder if the situation doesn't work out as planned.
In my admittedly limited experience, Silkies were put on this earth to be mamas.
