What are some tips for a designer to use Interface Builder effectively?

At Noctacam, an iOS app, we have 3 engineers (including myself, the founder), and a part-time UX designer. I'm trying to get the designer to use Interface Builder, and he complains strongly saying it's not a good tool for designers.

I agree and empathise, but I've tried to point out that if he wastes an hour more wrestling with IB, but engineering saves two hours, it's time saved for the team as a whole. It's the team's productivity that matters, not that of any particular individual.

The problem I'm trying to avoid is that design gives a PDF, or some other format that can't be directly used in an iOS app. This requires reimplementation, which is a massive waste of time. In a previous job, it took my team two months to implement what was in a 80-page PDF file, after UX took two months to design it.

Re-implementation also often results in lower fidelity. My designer complains about this exact same issue in his other job, saying that engineers implement it only with 60% fidelity, but he's unable to see the link with the tooling issue. This degenerates into a blame game where designers say engineers are not skilled, or have insufficient attention to detail, and engineers say that designers don't understand the constraints of the platform they're designing for or they timelines there are asked to keep to. I've been in multiple of these arguments and have no desire to recreate them again in my startup.

Getting the designer to use IB makes him aware of what's easy to implement and what's not, so that he takes that into account when designing.

Basecamp, for example, says that they skip Photoshop for UI design and go straight to HTML/CSS. I believe that's the same issue I pointed out, namely that of designers using different tools from what engineers have to use. HTML/CSS for Basecamp translates into Interface Builder for us, since we're an iOS app rather than a web app.

Have you as a designer ever used IB? What are some tips for designers to make effective use of IB? What workflow works, what doesn't work? Any advice is greatly appreciated.