I'm sorry you had to wait so long to get an answer on your question.
The reason most English Bulldog breeders use artificial means to inseminate and whelp litters is due to the shape of the Bulldog. It is difficult for them to breed due to their barrel like bodies and stout legs so to up the odds of a breeding taking, they opt to use artificial insemination. This is not to say the breed can not do this naturally...my bulldog came from a litter that was bred and whelped naturally, so they are capable of doing so.
Natural breeding needs to be done during the heat cycle normally between days 9-14 of the cycle. During this time, the female should allow the male to mount. Given this breed, you may have to help the male stay atop the female.
What you are describing in your boy while he humped the bear, they are called the bulbus glandis and this is an absolutely normal part of breeding...they hold the male and the female together until it naturally goes down..this can take 5 minutes to 45 minutes and the dogs should be kept still and calm during this period.
You can read more here: http://www.woodhavenlabs.com/males-swollen.html
So everything you are seeing is totally normal :)
Please let me know if you need further assistance.