I think you should go the extensions route. There's DIY kits that literally have you plug in the wires.
Personally tried sleeving myself. The tool to just get molex pins out cost 25 dollars alone. Then there's sleeving, lighters, heat shrink. And, the most expensive thing is time. Plus those molex connectors hurt to hold.
Please don't dip or paint your wires. I love plastidip too but I don't think it'll work.