Ok, watched it several times now trying to understand why you're doing what you're doing.
I did a few resin models (incl. my own moulds and casts) back in the days and while I agree that stripping off clear coated decals can be a real pain, I never ever would have taken a knife to scratch the details off. This seems brutal and is IMO just short of throwing this thing into a shredder. You just don't get those scratches and trenches back smooth unless maybe you sand it down completely out of shape. As a little suggestion, when you're trying to sand a surface back smooth, try wrapping the sanding paper around a file. You wont achieve a plane surface when only using your fingers.
I see you're using duct tape for the tail (?!?), why not a primer or and/or opaque laquers? Use the duct tape for removing the decals instead. Thoroughly press it onto your decals and then peel it off. The usual decal should come off together with the tape.
The model looks like injection moulded plastic (polystyrol or such) not resin. Is it really decaled or is it printed? Printed detail comes off easily with acetone but be quick on plastic/resin or try to figure out alternative solvents that aren't as agressive as acetone. Ethanol might do it if you're lucky.