Lighter fluid, dish soap and water, or rubbing alcohol first, then remove towards the back.
When reinstalling, from the back towards the front, first lubricating with one of the above.
My personal perference is Ronsonal lighter fluid, avaialable at your local drug or grocery store.

Out of curiosity, why do you need to competely remove the hoods, unless you are replacing them? They are as rare as hens teeth, I'd be concerned about damaging them.