Put several shapes in the same place, apply a lot of blur to the shapes, then apply blending modes to some of the shapes.
You can get some advanced effects with blob style gradients if you use blending modes. The interaction of the blur and blending modes produces some effects that are hard to create any other way. In the example below the overlay blending mode causes a sharpening effect where two shapes touch.
I suspect there are fewer than 5 people on the planet who know what will happen when both blur and blending mode effects are combined, before they try. For everyone else, it’s a case of “try until you get something you like”. So this can be time consuming.
