It is not very difficult once you have managed to create one.
It may take you a whole afternoon to create your first one, but after that when you know what you are doing, then you can knock one out every 10 minutes or less.
I used Gimp for my paint program. (Open source ....Free).
I don't know of any other free program that supports what is required and is easier to use
We all suffer the same problem.
To create our code we require the models.
Model creators will not help us until we have the code.
the old saying is so true "
Santa Claus helps those that help themselves".