You're in good company, and you're quite right - most data sheets completely gloss over this essential information.
The problem is that calculating the correct values for these components is very complicated, and depends a lot on the load, the output capacitance, the switching frequency and other parameters. There's no 'right' answer either, just trade-offs between stability, complexity and transient response.
Since you're using an LT part I'd highly recommend downloading and using LTSpice to simulate your design, and you can see the effect of various compensation components for yourself. Expect quite a bit of trial and error. Experiment with varying each part individually and see what effect it has on the stability of the circuit; once it's stable under all input voltage and load conditions then check the transient response.
If you find a quick way to get it "right" then do please let me know - but I normally start with an educated guess and then keep running simulations until I know the supply will be stable.
Then expect to have to change your values when you actually build the circuit, because no simulation is going to be 100% accurate!