If your culture isn't showing signs of life after 3 days, go ahead and start feeding. If, after a few more days, nothing happens, start over and place the culture in a different part of your home. We're not saying a stand mixer wouldn't work, but given the volume, an electric hand mixer is easier. If you don't have one, you can certainly use a hand whisk, but it's going to take some elbow grease and a couple minutes more to reach stiff peaks.