You don’t progress in cb persay, you progress outside clanboss and then bring your progression to cb. The efficient/subReddit approved thing to do is be in a clan that fits your clan boss capabilities and cvc capabilities, or be in a clan that you can grow into.

Normal and hard clan boss are not a place to spend any substantial amount of time in and therefore are not worth investing a speed tuned build for. Just progressing champions naturally for any other areas of the game will get you to brutal.

If the clan means nothing to you, leave it. Otherwise it’s no big deal, y’all will get there eventually as long as the clan stays active and populated.