Depending on the condition of the gutter I pull out a white bucket and dump some F-13 into it and then eyeball about a 20:1 ratio. I dip a brush in this and brush it on the gutters. I let it dwell for a few minutes and then agitate with the brush again and it usually comes right off. If it is stubborn I will add a little more F-13 to the bucket.

For Simple Green I use it full strength and Purple Power I cut it about 1:1 with water.

F-13 seems to do the best job and is the only one I use on gutters that look like the paint is failing or old.