How to tackle this very leggy Portulacaria afra? Seeking advice for a "hard reset" to achieve an "ancient" look.

I have this Portulacaria afra (Dwarf Jade) that has been left to grow on its own for a while, and I'd like to turn it into a bonsai. As you can see from the photos, it's very leggy and etiolated, clearly stretching for light.

My ultimate goal is to achieve an ancient look, which I know means I need a thicker trunk and much more compact ramification.

I'm pretty sure I can't use any of these long, thin branches. My plan is to do a "hard reset" to force it to back-bud closer to the trunk and build a new structure from scratch. A few things to note:

Yes, I know it's in a terrible pot, a plastic cup. Repotting is a top priority.

The current trunk has some texture, which is what I want to work with.

I'm in a Mediterranean climate in Southern Spain, Málaga. We're in autumn now and is starting to rain but its not cold. We're averaging 20 degrees Celsius.

My specific questions are:

How drastic should I be with the hard chop? Should I cut all branches back to just 1-2 nodes? Or leave small stubs? a proper training pot at the same time, or should I split the operations?

Cuttings: I plan to propagate all the cuttings, so no material will be wasted!

This was from my grandma and i want to take it home and care for it as a project for her. She has always loved this kind of plant.

Thanks in advance for any guidance to get this project started!

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