Can't say anything good or bad about your ideas, but I just finished
restoring a '73 1800ES ( It's for sale by the way).
The leather seats in it were hard as cardboard, and they needed dying.
I did some research ( Google research that is), and found Leatherique
cleaners, conditioners and dyes. www.leatherique.com
The conditioner is really good, but may take a few applications. My
seats are really soft now.
Then I cleaned them and used the Leatherique dye, and after a year or
so, they still look great.
I have no affiliation with Leatherique, just really like the stuff.
Ron
Ron/Champ 6
1963 8E5 Champ (Champ 6)
1995 VW Passat (Vanilla..yuk)
1994 Volvo 850 (Tilley)
1973 Volvo 1800 ES (Hyacinth Bucket)