Um..at the risk of sounding that I know to much...
...when 2 dogs (purebred) are mated, someone helps them "get it together"...keep it there...& to separate when they are done.........if you don't, the male can get REALLY hurt...if he does get hurt, he will not like doing that anymore then the boy dog is worthless...(farm boy 4H knowledge 101)
There is also "whackin' it"...if they use invetro to inseminate the female...the vet jacks the dog off...& sends the sample into the other vet, or the other part of the office for that part...(source, Ron White, "Um..how about, I just let you do that, he likes me too much already!")