This is a great idea, and I have thought about using the same soap throughout the testing, as well as shaving on the same schedule consistently. I use some traditional puck styles as well as sticks, and regular canned shave cream like Barbasol and Gillette Foam mousse. All of these will do what you mention for me. I had not heard of trying Williams pucks with distilled water. I will give that a try because I like the smell and cost of the Williams, and I have plenty of distilled water around. Thanks for the advice.Before you begin trying out all your sample blades, consider settling on a single soap for use with all of them to optimize your results. Soap can make or break the performance of a blade. A soap with residual slickness ( shave a pass, then rewet the area just shaved - is it slippery or not?) Many types of soaps & creams don't have that residual slickness that can have a positive effect on a shaves' smoothness or closeness.) For examples of good residual slickness, look at: Williams puck lathered with distilled water, TOBS, Stirling Soaps' Tallow varieties, Shannon's Soaps, or even (the slickest) equal parts of Cremo + Neutrogena for Sensitive Skin. Of course, there are many more slick soaps, but these are the ones I have the mose experience with and, listing too many more just complicates the task of deciding on the best one to use for Your test.
So, if your choice of soap/cream slickness feels like any of these, it will give you the best basis for comparisons between your blade samples.