Saturate under the chip by running water soluble liquid flux under each:
http://www.amazon.com/NTE-83-1000-0186-Rosin-Liquid-Flux/dp/B0089EQGW0/ref=sr_1_1?s=electronics&ie=UTF8&qid=1393111521&sr=1-1&keywords=liquid+flux+pen
Get one of these:
http://www.harborfreight.com/430-800-570-1160-interval-heat-gun-with-led-temperature-settings-69343-9184.html
Set it to about 850 degrees, and make a circular pattern over the larger chips for about 1.5 minutes per chip. Don't let the board discolor or you are too close. Stay about 3 inches away and keep moving.
Don't move the board for about 10 minutes... let it completely cool. Same result as a reflow oven, but only costs about $35 and you can use the heat gun for a lot of different other purposes... not a good idea to try and dry your wet hair with it! 
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