I think that could actually make it harder to get the bar through the stem. Simply prying the stem the right amount, and manipulating the bar in the correct orientation, you should get them apart without unsightly gouges. If something threatens to make overly firm contact then stop, think about how you got there and back out slightly - resist the urge to rotate the bar before you have slid it back a bit.
Don't forget that brake lever hoods and clamps can also easily mark the bar; sometimes you can't avoid little dings from the hood when the clamp is tightened, but avoid being careless pulling and twisting a loosened lever - it can be best to remove the body of the lever completely (rather than just loosening it) before removing the clamping band.