the old way was used to have another person place the 1 day to 2 week old lamb on it's hind end by holding one front leg and one hind leg in each of their hands, then another person would use a sharp knife to cut the lower 1/3 of it's scrotum off, then using one's both hands push out the 2 testicles, grab them with one's teeth and pull them out.
While this may have worked years ago I certainly do not recommend this today. You are putting yourself at incredible risk of infection - think worms/parasites, & everything else that is coming out close to where the scrotum is. It is not worth it.
... it grosses me out to even think of doing it that way.
Cowboys used to do this with calves too & recently someone, in the last year, died from the infection they got by biting the testes of calves.
Liz