Experienced target man Jose has gone nine games without a goal since his arrival from Spanish side Real Sociedad.
Club-record capture Silva, meanwhile, has not netted since the Black Country Derby defeat to Albion on January 16.
On the struggles of the pair, 306-goal legend Bull said: “I feel for them in a way, being a former striker.
“You feed off crosses coming in and balls into feet which you can work with, but they’ve been very, very sparse.
“I played with a strike partner for most of my career, and we would have chance after chance – week in and week out.
“That isn’t the case at the moment, so they’ve got to be patient.
“But when they do get the chance, it’s going to be one of the last chances they have in a game, so they need to be on the ball and have the eye of the tiger.”
Jose will hope to break his duck soon, with Wolves having the option to make his move permanent in the summer.
Teenager Silva – signed for £35million from Porto last summer – has looked the more likely scorer of the two in recent times but was unable to connect properly with a late header against Liverpool last week.
Bull added: “We can only persevere for so long, though, as they have had chances in the games, to win or pick up a draw.
“They’re just not taking them. Whether they’re getting fed up, I don’t know.
“It’s frustrating for them, but they’ve got to really knuckle down.
“Hopefully, one of them will get a lucky goal somewhere and kick on.”