Weeds are best controlled when they are actively growing. The toxicity of weed killers act on the leaf tissue taking it down through its system to the roots where it causes injury and death. If the weed is dormant, it could take much longer for the toxicity to be drawn into the leaf. Same reason why water is not so much needed during winter---the plant is unable to take it in. Considering the cost of herbicides, it does pay to get bang for your buck. Wasting it on something that cant appreciate it is money and effort wasted.

No, it will not make your grass brown if used properly (read all labels to make sure it will work with your grass). Weed B Gone will also not kill clover. For yard weeds I mix Weed B Gone Max and Weed B Gone Clover, Chickweed, and Oxalis Killer in a tank sprayer using the appropriate amount of water. Then about 2 or 3 days after mowing I spot treat any weed I see, using the mower lanes to keep track of where I have sprayed. If your yard is totally infested you can use a hose end sprayer, but this uses more herbicide, and doesn't apply it as well as the tank sprayer, but it still works.

I think you probably want to do it the other way around. I haven't used Milorganite, but I thought you were supposed to water it in right after spreading it. If you spray WBG, you're not supposed to water for a few days after doing so. Actually, what might work the best is to apply the Milorganite, wait a week or so for it to kick in so the weeds are growing really well, and THEN hit them with WBG. WBG works best when the weeds are actively growing.

johnuch, I know my advice was just "baby bear" (not too hot, not too cold, but juusssstt riighttt) but it sounds like you did it right. Yes, clover can be difficult. See what the package says about when you can follow up with another spray and do that: it is harder to kill clover now than in the fall, so you will probably need more than one spraying, at the "baby bear rate" each time. ;-) Keep hitting it at the recommended intervals until it is gone.