P: Increase the strength of the blur tool.

If you could save your blur tool settings into a tool preset file and share that, I'd love to try it out. 🙂

Yes, that size high res. I should clarify that my solution is to increase the blur strength significantly, but not blend like watercolour as i don't think the blur tool is the right kind of tool to create his effect even if super strength was added. 

My CPU ain't crawling. 

When I use your settings I get a little bit of blur. Nothing more than I normally get with blur strength at 100% without scattering, and unfortunately nowhere near enough for the color blending effect the original poster is after. Are you sure you're listing all the settings that are creating your blur tool's behavior?

Also, setting the scattering count to 16 will slow almost any CPU down to a crawl at larger brush sizes, doesn't it? When you say it works on a high res image, are we talking anywhere close to 4000x4000 and above?

I'm doing a scribble across or wave back and forth across my edge that i'm blurring by the way. 

Yes, the post is about the blur tool. There's a huge amount of blur strengthening when i adjust these. This will vary depending on the size and resolution of your image though. You need to make sure you have done scattering plus transfer plus shape dynamics settings

I'm sorry, maybe I'm misunderstanding you, but are you talking about the blur tool? Scattering doesn't seem to increase the blurring effect beyond what it normally is.

The smudge tool, on the other hand, does have a blurring effect when using scattering. Is that what you're referring to?

SOLUTION:
Brush Panel > Shape dynamics = Control > Pen pressure Min diameter 100%
Next: Scattering > Scatter 135% > Count 16
Next: Transfer > Strength jitter 93% Pen pressure 100%

That should give you a decent blur on a high res image but obviously, have a play around with those settings and see what works for you. 

You're welcome. 

The real Problem is not that it's not strong enough. Try blurring an Image of 300x400 pixels, and you will find it has a pretty strong effect. The true problem we face here is that the effect is actually depending upon image resolution, so the bigger the image the weaker the result. Having images at resolutions of 3000x4000px and the tool hardly has any effect at all.

This is NOT (as fanboys claim) by design, this is sloppy programming! For the tool to be useable the strength of the effect should be automaticly adjusted to give the same visible result depending on the size of the brush NOT the resolution of the image. If you want "subtle" blurring it should be adjusted by the strength-parameter.

It would be nice to have an extra field so you could adjust the pixel amount of the blur tool, like the gaussian blur function has.

As have we all. When my CC subscription expires I'm going to find apps that better meet my needs.