Call the gym leaders on the pokegear once you get their numbers and go to seribii.net to find out when and where you can find them.
Mt. Mortar.
He won't come out.
hoo nos
in Johto, Safron after you defeat red!
You must find them somewhere at a certain time then you get their phone number. After that call them on a certain day and they will meet you at the fighting dojo. YES FOR ONCE HIS ANSWER IS RIGHT ^^ JK!!
In one of the caves in Johto I think he is at mount mortar beat him and you get a Tyrougue
Get the numbers of the gym leaders and call them for rematches, where they'll be available in the Fighting Dojo. A gym leader will stay in the Fighting Dojo until you rematch them, so you can have all of the gym leaders there. It can take a while to get the phone numbers and call all of them when they're available for a rematch, but it's better than fighting wild Pokemon (the highest you can fight is level 50 at Mt. Silver). In addition, you can call trainers that you have the phone numbers of for rematches during certain times of the day.
The Fighting Dojo Master is in Mount Mortar in the Johto Region. There are three entrances between Mahogany and Ecruteak, so take the middle entrance (and have rock climb and surf) to get to the dojo master.
After game-Elite 4 rematches, Gym Leader rematches, etc
In kanto (Saffron City)
Daisy gives massages from 3:00-4:00 PM. You can give a Pokemon a massage once per day. It's also necessary in order to get Blue's number for rematches in HeartGold and SoulSilver.
In Pokemon Gold, Silver, Crystal, HeartGold and SoulSilver the Fighting Dojo Master can be found in Mt. Mortar. He is found deep in the mountain past a maze. Try to have an empty slot in your party as he will give you a Tyrogue for defeating him.