All your suggestions would make the weeds grow faster and thicker. The most organic way to deal with these weeds would be to pull them or how them out. The dandelions will need their taproots removing. If they are in a lawn, low mowing would stop them flowering and seeding.

We are using the Fiskars Uproot Weed and Root Remover but are hoping to supplement this with other methods. what is your opinion on corn gluten meal?

I'm afraid I can't help you on the cgm. I've never used it and have never known anyone use it over here. Nor do I know that Fiskars tool. I just use my hands, a normal garden fork, a hand fork or a hoe for weeding. I hope a US poster can help you on those things.

Corn gluten meal is a pre emergent weed control that can be effective when applied properly. Applications need to be made before seeds start to germinate but not too soon and it has an effective life of about 6 weeks. For my area of the world, west central Michigan, we are told to apply CGM about when the Forsythia blossom.

CGM stops seeds from rooting but does not stop plant growth from already established roots.

Take a good, in depth, look at the soil and correct any problems that may exist for the plants you want to grow in that soil. Look at those unwanted plants and learn about the growing conditions they prefer and, if possible, change those to reduce the likelihood the plants will grow.

kimmq is kimmsr