Using the blur tool - no visible change

From what you have told us, the Blur tool might not be the best fit. The important thing is that you view the results at 100% zoom ratio.  The example below is a single pass at full strength showing before and after.

Try ussing one of the blur filters, like Gaussian blur.

If you need to blur a particular area, the Quick Mask can be a good choice for selecting it

Hit Q, paint in the area, and hit Q again to exit QM

A big advantage of using a filter blur rather than the blur tool, is that you can make the layer a Smart Object, and apply the blur nondestructively