Which type were they Leon?
I was issued two pairs of the old DMS ankle boots back in the 80's and have used a variety of service boots since then.
With the high leg boots of the 90's the Non-parade boots we just soaked them in very hot water for 30 minutes, then walked them dry over the course of a day, usually needing a change of socks at some point, then a good few layers of quality boot polish and they are good for a few years of hard work.
I dont know who actally made them. I was issued a pair to break in before before RT in 2010. Like you say I bathed them in hot water, worn them wet, forced dubbin into them best I could and worn them for one month, reapplying dubbin throughout. Bloody things were still stiff as a board 3 weeks into RT. Strangely the second pair we were issued at the start of RT were no where near as bad.