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Well, the best way to use the HRCC is to optimize one eyepiece, whichever one that is. Play with the settings until you get the star images good up to as close to the field edge as possible. That will be your focuser's setting for all eyepieces.
Then, insert a second eyepiece and focus with the helical top of the HRCC. Don't move the focuser at all. Whatever setting of the HRCC top is required to achieve focus, THAT is the setting for the HRCC with that eyepiece.
And, repeat the above with every eyepiece in your collection. The helical top of the HRCC will make your entire eyepiece collection parfocal. There may be an eyepiece whose focus requires pulling it slightly out of the HRCC. Pull it out of the HRCC until it focuses. This may require an eyepiece barrel extender (like the 8 and 6 Ethos in the Paracorr when they're used as 2" eyepieces). There may be a couple eyepieces that require a more in-most setting of the HRCC than the top allows. For these, you have no choice but to refocus using the focuser. Overall, though, it's unlikely to need more than 2mm of focuser travel to optimize all eyepieces.
if you have the type of focuser that is a 2" focuser and uses a 1.25" adapter for 1.25" eyepieces, that is all you need to know.
If you have the type of focuser where either a 2" adapter or a 1.25" adapter is held in a ring on the top of the focuser drawtube (some Sky-Watchers have this), note that the ring on the focuser has slightly less than a full 2" inside diameter, so the coma corrector bottoms on the ring. This means a lot of in-travel of the focuser is needed to get to focus. If this is your focuser, hone the ring out to 2"+ so the HRCC, when inserted in the 2" adapter, bypasses the ring entirely and sits on the top lip of the 2" adapter. This would gain another 1.5" of in-travel if this is your focuser type.
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