... and there we have a typical SOC non-answer to a question. The OP did not ask "if" he should do it, he asked "how" he could do it. What you did and your opinion on what's better is not what he asked for.
Can we stop doing this? If we hold true to form and wait long enough, we'll have a few posts from guys who've never done it about how they would do it, if only they would do it, you know... someday.
My car was built as a coach, and has the umbrella E-brake. The E-brake came already done on the car. It was important to me at the time, and not at all now, but that's OK. Henry from Intermeccanica used a 356 umbrella handle and locking mechanism, and built his own bell-crank with a piece of steel round stock and a couple pillow-block bearings mounted on the beam with muffler clamps. I can snap a picture of that, but it's not what you asked.
The penetration through the firewall is a piece of tube-stock caulked in place. The cable attaches to the bottom of the umbrella handle mechanism and comes out the tube and then attaches to the bell-crank. There are no seals of any kind, but I've never experienced any leaking.
Here are the pictures:
They’re not great, but let me know what you need and I’ll try to get it for you.