I've been using similar drops just for maintenance cleaning. I put a couple drops in their ears, gently massage at the base and let them shake it out. I don't squirt it in her ear, I just do a couple of drops like you would do eye drops for your eyes.
I know someone whose dog had an ear infection - the vet gave them ear drops and instructed them to do this as well to keep the ear canals clean.
You can find the powder at your local pet supplies store. They use something called a hemostat for deeper hairs, I've used tweezers with no problem, but then again my dogs sit very still for me. Be careful when using anything other than you fingers to pull out the ear hair.