I agree that quarantining is the best way to handle new fish. That's the best thing you can do to prevent diseases from coming into the main tank. Since ich is now in your main tank, I agree that the higher temperatures are the best way to treat it. Some of those ich meds may stain your tank silicone, plus they are not effective at all stages of the ich as explained below. I would also be very hesitant to induce stress in a fish while treating a disease. The fish are already under stress and may not be able to handle another stressful situation.
The ich parasite has three life cycles or stages: on the fish (the only stage we can see), free-floating in the water, and in the gravel. The ich falls off the fish, floats/swims through the water, and falls to the gravel to reproduce. When the ich is on the fish or in the gravel, it encapsulates itself so that meds are not effective. The only stage that meds are effective is the free-floating stage. However, heat is effective at all the stages. Raise the temperature to 87 or 88 degrees and keep it there for two weeks after you see the last spot. This extra time is important to make sure all the reproduction activity is finished.
Heat is also effective at treating the whole tank. Removing one or two fish to treat won't help eliminate the ich that is in the water or in the gravel.
Ich reproduces rapidly at 85-86 degrees. As you move through that temperature range, you may see an increase in spots. Try not to linger in that temperature range too long. The ich begins to die at 87-88 degrees, so try to reach that temperature range as quickly as you can without stressing the fish. As a starting point, raise the temperature one degree every 6-8 hours.