Gimp is a very hard program to use if you dont know how to use it..
The lack of photoshop tools makes it a little difficult at first.
For a simple face swap there are a few different things you need to do.
If you use photoshop you should know that the quick selection tool and the lasso tools make selecting things quite easy. with gimp you need to use the Pen tool
After you have it all selected you need to copy the piece you would like to swap, and then paste it onto the other work.
Next you need to use the rotate tool to line up the eyes nose and mouth, also you need to take the opacity down on the layer you are rotating to have a more precise line up.
You also need to use the scale tool sometimes if the face is oblong and you need to line up the eyes ect..
After you get everything lined up you need to cut out all the extra picture from the new face. I like to lower the opacity of the new face if i need to cut out part of the face so a bandana (or other objects in this example it is a bandana) is lined up. You need to use a hard brush at first and then you can use a softer brush on lower opacity to make things "look nice"
Now you Need to get a harder brush and cut out all the parts of the new face that is not needed, because you are going to adjust levels and hue later.
Here you use the hue and saturation to adjust the color and saturation. You d o this so everything matches up very correctly.
After the levels ect.., are adjusted, you need to to take a soft brush with very low opacity and go over all the areas that just don't look right this is a crucial part of face swaping.
After you have done all that you should have a final product that looks something like this
Linear Mode
