Yes I was an industrial electrician for the last 20 years before getting laid off in January. If you have a 100Amp panel now, you should have a 200 amp meter base. It would be a case of buying a 200 amp breaker panel, which should cost around $110-130. And having your power cut to the house for a day while the old 100 amp is removed and the new one is installed. This will give you 100 amps to the house, then you can run a 100 amp breaker and wire to your garage giving you 100 amps there. If you went this route you would be out the cost of the 200 amp breaker panel, and 100 amp panel for the garage (heck you could use your old house 100 Amp) and the wire.
Then a 50 amp or whatever size required breaker needed for your new flash. Depending on the length of cable you could DIY this for $200 safely.