The easiest and cheapest method is to just not worry about it. You could spend a couple hundred bucks to drop a pound off the bike, and honestly never notice a difference. In my experience, a bike doesn't start to get unwieldy until it's north of 30lbs.
Weight weenies are usually okay with $1 per gram of reduction, and as someone who once upon a time worried about bike weight, you usually end up lightening your wallet more than the actual bike.
Not to sound like a typical N+1 guy, but If you want a lighter bike, buy a lighter bike. I have two bikes that are ~7lbs apart. The lighter one is a little easier to ride faster. But I ride the heavy one more often-- almost twice as often. Weight isn't everything.
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