Jack Skellington inspired, Tron, Darth Vader, Jack Skellington, Offspring logo, Nerf logo, Nightmare Before Christmas Pumpkin Hill, Jack Sparrow, Cheshire Cat, Fallout 3 Vault Boy.
(2006-2010)
Feel free to ask any questions.

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The best way to go about it is to draw out the design on the pumpkin, and to have in mind what areas you want to scrape so you only have some light show through. Those areas I cut a deep gash (but not all the way through) with the exacto knife. Then use the scraper side of the carving tool to scrape out the design. Going through the design with the exacto knife helps keep the scraper tool more accurate.
Some of the thin lines (like on Darth Vader, Tron and parts of Jack Sparrow) were done completely with the exacto knife since the scraper end too wide for some details.
I honestly don't know if it'll work on those pumpkins. I've never carved one let alone picked one up.
Keep in mind too, that the inside walls of the pumpkin you intend to do the shading (scraping) on need to be quite thin in order to be visible. This either involves magically finding a thin pumpkin, or manually scraping out a lot of pumpkin guts.
That may help with the Michaels pumpkins, if they're pretty thin (like 1/2 to 1 inch) I say go for it. The light will probably shine through.
And an exact-o knife sometimes.