For nonlinear circuits (amps, filters) I'm working towards using HSIM: (https://www.researchgate.net/publication/354894471_Multidomain_modeling_of_nonlinear_electromagnetic_circuits_using_wave_digital_filters)
Essentially breaking down the tree into smaller sections and solving nonlinearities locally. A bit different to Kurt Werner's suggested approach of grouping the nonlinearities at the root. Apparently this way is the most efficient (with SIMD), but nobody has compared them yet, so I am looking into doing that and writing a paper.
Apart from that, yeah your process is similar to mine.
Creating models for each component, using iteration to inch closer to the benchmark results from the real component. After that you have to deal with representing the connections 😂
Lots of work. WDF is good if you know electronics, state space modelling (+MNA) can be tidier and a heck of a lot less code, but I find it more confusing. I've only done filters using such techniques but I know that it's the industry standard.
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I'm working on a WDF header library for Hise which I intend to release, but it's still in progress, I need to talk to Christoph more about SIMD support in Hise, to see what the best way to optimise it.