I wouldn't breed a White Silkie to a Black; As
@The Moonshiner states, White Silkies are Recessive White, and often based on e+ Wildtype, rather than Extended Black; you would be messing up the e-series, which I would suggest not to do.
As your two current hens are Paint (Extended Black based, I assume; white with black spots, not red), and Black (Also Extended Black based), I would be going for a Black, Blue, Splash, Dun, Khaki or Chocolate; basically anything solid coloured is Extended Black based, so long as that colour is not White or Red/Buff.
ETA: A Black cockerel over your current birds, as an example, would produce 1/2 Paint chicks and 1/2 Black chicks with the Paint hen, and all Black chicks with the Black. The introduction of a dilution gene such as Blue would change the ratios, however as you're still within the e-series, it doesn't matter; they would still be considered pure for their variety.