I've never done the caustic soak, so can't offer specific advice on this issue, but I have preserved olives for a number of years, so can offer some principles that mght guide your actions.
There's essentially two things you are trying to achieve when preserving olives - remove the nasty bitter flavours, then preserve the olives for future eating.
From my reading, there are three ways to remove the bitterness
1.chemical neutralisation - caustic soda, I think woodash does the same thing.
2. leaching - this can involve a range of methods including dry salting to remove lots of the moisture, then fresh water soaks; slicing the skin then a couple of weeks of soaks and rinses , smashing green olives(the bottom of a full 300ml beer bottle works well - drink from a separate bottle, tho
then soaks and rinses, which is the fastest method and can achieve edible olives in a week or so.
3. lactofermentation, which involves placing fresh washed olives in a brine solution (I use 10% by weight), then waiting for a couple of years while the fermentation removes the bitterness (I not sure how this works, but work it does). Mine were edible at about 18 months, but still had a bit of spritzig on the tongue at this stage.
The leaching method removes the bitterness, but also removes some of the flavour compounds, the 2 year method results in lovely flavoursome olives, with a richness of flavour I've not found in other olives, but it's a long wait.
I've read that placing a cut lemon or two in the mix adds citrus overtones, and the change in pH is beneficial, but I can't remember why - reducing mould growth, perhaps?
Preserving the olives can either involve brining, vinegar, (or a mix of both), dry salting, or just pop them in a ziplok bag and freeze them.
If your olives are now not too bitter to eat, I suggest they are ready to preserve, tho I'm not sure how the dilution/removal of the caustic works. Not having tasted caustic soda, I'm not sure how you would tell.
My recipe for final preserving is a quarter of a lemon, a small dry chilli, 10% salt solution, and whatever dry herbs are around - basil, oregano, bay, rosemary, etc. Use dry herbs, there is a chance that wet herbs might include sufficient moisture to breed nasty bugs.
Brined olives can be preserved under oil (olive, naturally) but excluding oxygen with damp foodstuffs is a bit tricky - I avoid it.
They can also be pickled in vinegar or acid solutions, but I've never tried it.
So picking olives now, you are southern hemisphere?
T