I wanted an easy way to generate skeleton patches for all my plugins, so I wrote a python script.
For the script to work, you need to install python-ladspa.
I have generated all the patches for my system, so for most people, you won't even need to generate the patches. They are located in the ladspa dir (install this in a pd lib dir).
You can check out how it works with demo.pd. demo.mid is a seq24 midi score.
plugins.txt is the info that the script spits out, when you run it, you can use it as reference when making your own patches.
You will probably need to fine-tune the generated patches, because the ladspa meta-data for control inputs isn't always accurate and sometimes a toggle is better then a slide, for example (see demo.pd for a few examples of tuned patches).
My demo patch also illustrates using midi record on/off messages.
The demo is simple and pretty noisy, I just threw it together.
I couldn't figure out how plugin~ ctlout's work, so I left it out.