Help with Layers

Greetings forum,

Can someone tell me how to blur the edges of a mask layer??

I have tried adding a layer in between the mask layer and masked layer and then copy and paste the mask layer “cut-out” to that layer, then use the radial tool in the color mixer color with white and grey. This doesn’t work.

Does anyone have an idea of what I am trying to do and if so, is there a solution out there??

Thanks in advance