W11 Gimp Transplanting Faces

This week I'm creating two new photos from a mixture of Sarah and Mark. The results should be one of Sarah with Mark's face and one of Mark with Sarah's face. I'm using instructions from a previous post...

Gimp video Tutorial for transplanting faces
http://www.youtube.com/watch?v=CsQBKYtIc7g

...and another with written instructions...
http://www.tutorialized.com/view/tutorial/Blending-Faces/17474

...and finding out where various tools are using user manuals created by Gimp fans rather than the official Gimp manual - which is dire. The principal tools for a transplant are:

Transform tools: http://www.designyourownweb.com/gimp/transform-image-gimp.htm

Layer Masks: http://gimp-savvy.com/BOOK/index.html?node44.html

As the rotation and size of the images is pretty similar, my chief 'transplanting' issue in these photos is Mark's beard! In the Mark on Sarah photo I need to eliminate everything except Mark's features and keep Sarah's skin. On the Sarah on Mark photo the situation is reversed, I need to eliminate as much of Sarah's skin as possible. To remove skin I make sure that black is in the foreground of the mask and to put skin back from the original layer I toggle back to white as the foreground. This means it's easy to do finer and finer work choosing exactly what I want to keep and eliminate.

Colour Matching:

Our skin tones are extremely different so I selected the cut out layer - not the mask - and then Colors, Color Balance. I altered the settings for a better match. Here I had to think about what I was seeing: what tones are in Sarah's skin and what colours are in Mark's skin eg whose has more red (ie pink) on the midtones or who has more green and so on.

For the Mark on Sarah photo this changes were:

Midtones +52, +31, +4

Shadows -28, +7, +13

Highlights -1, -16, 16

...and then altered the Hue-Saturation

Hue -5,

Lightness +10

saturation -3

Blurring edges between layers

I used this tutorial: http://www.gimptalk.com/forum/softening-the-edges-of-your-cutouts-p268828.html

The edges of the cutout layer are very sharp, so even though colours might now be similar the illusion is ruined! Select mask - not cutout layer - then Select, Shrink and 1 pixel. Then Select, Invert - so only the edge of the mask will be blurred. Then Filters, Blur, Gaussian Blur. On the Mark on Sarah photo i used 200 px blur!

And that leaves us with the beard issue! I've used the heal tool, but I really want selction from the Sarah layer to use on the Mark mask layer and that doesn't seem to work. What I've ended up doing is blurring and lightening the Sarah layer around the nose which leaves a 'five o'clock shadow' effect.