A good way to build strength in the arms is to pick up say the 20kg, do as many as you can, then move onto the next one down, do as many as you can, and so on, greatest effective way to build strength

You mean go straight on to another arm exercise after you have completed a set of the first? there is a particular name for that sort of training, I forget what it is called...

I usually go with weights and work my way up instead of down.

I have heard of working your way down as well, there is indeed a specific name to it, but I cant seem to think of it. I have never actually tried this though, I will have to give it a shot.

From what you described...I think you are speaking of "Circuit Training." Its a popular form of training methods thats used by the army, navy, sports teams, and competing fighter's alike. Circuit training is effective, and is bound to improve one's strength and aerobic fitness level.

Descending Sets.
Very intense and quite efficient. You can see Lou Ferrigno do them with bicep curls in "Pumping Iron" in preparation for an upcoming Mr Olympia Contest.

This is truly the best way to do your arm strength training. Circuit training can build your arms fast. It is important as the OP stated that you go from high to low. You need to warm up your muscle with a low weight but do not go to fatigue. Than you need to lift 80% of your highest weight that you can lift one time. Go to fatigue (the point where you cannot lift even one more) than go down 5 % and keep doing this till your arms are totally fatigued. Do not do this more than twice a week or you will damage your arm muscles.

This workout can be done on other body parts also.

is this the method that was invented in Russia?

My advice would be not to aim at building your arms up, but to work on the toughness of your hands. The bigger your arms are, the slower you punch. That is why I think that you should punch the bag for 15 rounds a day, without gloves. What that will achieve is tough hands and punching endurance. I advice you to work mostly on speed and toughening up the hands. That will build your arms up enough. See my post on workouts.