Unless strawberries are fresh and in season where you live, I would recommend frozen strawberries, they are usually pretty darn sweet. And one other little tip, if you don't want it to overpower your beer flavor, using thawed frozen, I would use one half pound per gallon. Also consider this idea, sterilize some cheese cloth and hemp string in boiling water. Place the cheese cloth around the bottom of your racking tube, tie it closed around the tube with the string leaving enough length to drape the string over the side of you bottling bucket or keg so you can easily remove it if it slips off when taking it out. This will take any particulate from the strawberries out before you bottle. I would love to hear and see how it comes out. Good luck!