Don't believe everything you hear about film speeds.
Yes, HP5+ is a low contrast film compared to some. In 35 mm, it has no antihalation dye in the emulsion. The base has a neutral density of aout 0.2 which has no grain, cannot be removed, but causes only a little more printing exposure. I would not hesitate to use it at 400 with proper metering.
Why saturate the emulsion with water? I don't remember Sandy King recommending that. Try printing with graded paper rather than VC, and use grade 3. If there is any detail in the shadows, it will show. If there is some detail, you can use a technique of bleaching and redeveloping to add more dye image. Use a rehalogenating bleach. A teaspoon of potassium ferricyanide and a teaspoon of potassium bromide in a pint of water will do the trick. You will know when bleaching is complete. Rinse well and redevelop in a rather strong pyrocat solution in room light to completion. In fact, you can use a teaspoon of catechol and a teaspoon of sodium carbonate in a pint of water as a redeveloper if you wish.