Hi Adam,
For what its worth, I have been using Round-Up and other glyphosate products for years around my bulbs, to kill off invasive African grasses. The areas I have to cover are too great to use paintbrushes. I use a small several-gallon sprayer which I can direct quite well. Collateral damage is minimal. The important thing is to remember that glyphosate only breaks down in the presence of oxygen, so it is important not to let it get into solution in the soil, where it might last long enough to kill something you like. Just spray the foliage, not the soil, and don't do it when there is a chance of rain.
In our rain forest reserves in Ecuador we use Round-up to kill off grasses in pastures that we want to reforest. We have done this on a very large scale with no ill effects. It is wonderful to see the rain forest trees seeding themselves into the pastures the moment the grass dies. I am a big fan of glyphosate!
Lou