He can wait for the blow jobs. Contrary to what Spike might believe, he does value more than just sex, and although he might never admit it out loud, the advice and companionship Spike's giving him right now are worth more than sex.
"I know. It's just something we've never really done." He lifts his eyes to Spike's face. "Sometimes I worry there really isn't any more to our relationship than working together and sex."