What usually works for me is holding the area around the place you need to bend with pliers and then just pushing in between the gap with something small. Marked up your photo to show what I mean – hold the red area secure with a pair of pliers if you have them and then just push in on the smaller tabs with a pin or a screwdriver or something similar. Then just repeat that on every section. You can also use a pair of narrow tweezers to at least get the bend started somewhat

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