Proper Ventilation

Live in the northeast. Western PA. Remodeling daughters house and everything down to the studs. Currently there is a ridge vent and 2 gable vents, North and South and no soffit venting. there are 2 bedrooms on the second floor with forced air heat and AC. I understand that my best option would be to put in soffit vents and baffles to the ridge and close off the gable vents. My question is this. My plan is to insulate the bedrooms walls and ceilings and seal off air leakage (wiring, vent pipes, etc.) put baffles in the rafters and insulate the rafters up to that point, not the whole way to the ridge. Then when I get the time i will put in soffit vents. This could be months from now and I need to start getting the drywall up. Would it be feasible to close off the gable vents somehow from the outside of the house after adding the soffit vents so that i can get things moving along. Once I drywall i will no longer have access to the inside of the gable vents.

Thank you

Proper Ventilation