Even if you successfully scrape all of the ice off your windshield and have your defogger running at full-blast, you still need a fully functioning washer to clean away all the salty slush that will inevitably get splattered onto your windshield. Because washer fluid is water based, it expands when it freezes, possibly cracking the reservoir. To thaw frozen washer fluid in your vehicle's reservoir, you'll need a combination of chemicals and patience.
M/F Place a sealed bottle of methanol-based windshield washer fluid in the bucket.
M/F Place the bucket underneath the faucet of a 2-foot-deep sink. Alternately, you could use your bathtub.
M/F Run hot water (no more than about 105 degrees F) into the bucket, allowing water to continuously overflow out of the bucket and empty into the sink drain below. Basically, this increases the rate of heat transfer.
M/F Stop the water and remove the bottle after seven minutes.