How do I get acceptable water pressure when using two faucets on my 1/2" water main?
1/2" is a very small "main" - the only truly functional approach would be to upgrade it to a larger main.

If your multiple-water use scenarios are of short duration, you could get some benefit from placing a pressure tank (as used in well pump systems) in the house to provide a few gallons of buffering, but after a few gallons (variable with size of tank and variation in pressure) the stored water runs out and you are back to what the main can supply.