By how much did it lessen the DA pull?
It depends on a few things that are particular to your revolver. You can use a very thick punch to reduce the pull to .5 lbs but then it won't have enough force to ignite a primer so how low it goes is irrelevant. The key is to get all everything in the revolver set up for ideal friction reduction so you can get the spring down as low as it can be and still be reliable. This varies somewhat by each revolver.
To use the spring bend process outlined in that book you'll be limited by the internal polishing/finish of your particular python. There are some tricks to reducing the stacking in double action but in a python it's all about balance, one change will affect another part of the action.
The new ones are easier to work on because of the simpler action but there's still a balance between the main spring tension and the trigger return force required to reliably reset the action. This balance is tricky because in the Python they are the same spring. In a Smith & Wesson or really any other revolver, a gunsmith can first polish all the internals so they can install or modify the trigger return spring so it imparts the least amount of trigger opposition to the finger. This directly comes off the trigger pull weight. Then they'll tune the hammer spring / forces second to get the final trigger pull down.
For example, as long as the trigger will return reliably with say only 1lb of spring force at the trigger after pulled, the additional force to release the hammer may have only be an additional 1.5lbs if the sear is set right and the hammer spring is reduced. Combined, the felt trigger pull would be 2.5 lbs.
The key then is getting that hammer spring down lower and still be able to reliably set off the primers. Some competition revolver guys have this set as low as it can go and only use federal primers which are the easiest to set off. I've seen some PPC guns that wouldn't set off a single non Federal factory or primed round but are 100% reliable for competitions using the right ammo.
Ensuring minimal friction to the hammers movement will help get the main spring force down as well as reducing any designed opposing forces to the hammers movement such as the firing pin return spring (very minimal) or transfer bars/hammer blocks.
