I agree you should probably have your vet show you the first time. It's not exactly difficult, but it is tricky to get the hang of "squeezing" in the right spot.
Warning though - it is the worst possible smell on the face of the earth
. If you do decide to do it at home, do it in the bathroom with papertowels close by (warm wet ones too to clean your dogs behind) and airfreshner for afterwards, it's nasty! We always used these aloe wipes for the area afterwards also to sooth since it's not the most comportable thing for the dog (as I would imagine
) Most dogs don't need it done, but for whatever reason, some do. You're dog is showing classic symptoms though.