Modding Machine for Pigs is almost the same as in The Dark Descent (meaning, the most of other HPL2 wiki pages still apply). You can use the scripts described in the rest of the HPL2 section, however there are some things which are specific to MFP and will be described separately. Make sure to get the editors from the Tools page before you begin.
The only way of modding which doesn't edit the base files and is easy for users is a Full Conversion. You can download the mod template here.