[*paul_moss]

Yes and  no Nigel.
The  top  colour that is on pigmented leather is basically a acrylic paint and the finish you put on top of that to protect the paint to stop it coming off is to put it in simple terms like a varnish you put on wood,the difference with the finish that you put on leather is that it is more durable.
The hardest part of applying the finish to leather is matching the colour but once you get used to the colour matching you can do it quite quick.
To apply it is easy , first you must remove the existing finish then you can apply more paint,this can be done with a spray( air gun) or sponged on with a dauber or sponge and then dried with a hair drier and it may need a couple of coats, but it takes only a few minutes to do.You then apply the clear finish over  it in the same way and that too takes only a few minutes.Depending on the type of finish sometimes you may need a bonding agent for the paint to adhere.
But as Judy said in an earlier post understanding the finish is were the training bit comes in.
The application is straight forward but just needs plenty of practice.

[LTT Leathercare]

The process Paul describes would be very straightforward on a single colour pigment and as he says takes practice. The colour mixing is the hard part but there are systems that can teach you how to do this.  Small repairs can be done with what we call bonded colour which has an adhesive agent and a finish in the colour which means they do not have to be finished over the top (although a quick spray of finish once you have completed your work never goes amiss). 

If you are recolouring larger areas you need to use a different product.  These days there are very good systems which do not require all the stripping down and work without bonding agents so the process is much simplified.  However you always have to be sure that a strict cleaning process is followed as pigments will not adhere to anything which has grease or oil on it.  (another reason for not using oil/wax based finishing products on pigments).  This product can also be used as a touch up product but always requires finishing over the top.
We have worked now for 2-3 years with this product and have had no failures as far as finish goes, many of the bonded products which have been used for recolouring have failed.

Single colour pigments as I have said are very straight forward to deal with (with the right products and training) but the problems start when you get 2,3 or even 4 tone pigments (ie. ones with more than one colour) and those with tinted finishes (ie. the colour is in the finish)  These make the whole process much more tricky and whilst there are tinted finishes available, the colour matching process is made much harder.

Hope this helps