Four days is not nearly long enough...don't worry so much about pollinating your females by accident. If you check on your plants every day (or even every other day), you will be able to spot the males long before the pollen sacks open. Even after i see flowers that i suspect to be male, i leave them for another five days or so, until they start hanging down...by then you can be 100% sure its male, and also see if it produces trichs, like some rare males do. If I just pulled plants the instant I thought it looks male, I would have wasted a number of good females...Give it another week or so...
