I had to give my BP oral medicine to treat any internal parasites just in case. My vet is a specialist herp vet and she never gave me a tube to administer it. For one, the syringe they give you should be plenty enough. If you mix half the dosage with half water it will make it much easier. I gently massaged the corners of the mouth until he finally opened them then in went the syringe. Slowly inject the dosage and rub on the neck before you take out the syringe to make sure it swallowed it.

You probably have this solved already, but just wanted to give you my input on how I did it.