Back in the good ole days, Diazinon was the one thing I used but is no longer available. If you want to try a commercial product rather than homemade remedies, I use this stuff called Ambush made by Willson. It can be sprayed on ornamentals, fruits and vegetable and I use it regularly for controlling aphids.
As far as slugs in the hosta's, I bumped into my neighbor the other day and he mentioned about putting onion bulbs all around the hosta's to keep slugs away. Not only do they keep the slugs away he said, the onions can be plucked and eaten when they've grown.