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"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
If you don't clean and scuff up the existing finish before applying the third coat, it won't last long........same if you apply paint that isn't compatible with existing.
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Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Appears to be too simple. But remeber, each coat add on to paint thickness. This will reduce motor heat dissipation and hence may affect performance. If motor capacity is big, design allowance would be too low, need to be extra careful. Confirm allowable and available paint thickness with manufacturer, before going for extra coat.
By the way, why do you want extra coat? Is that a a normal practice / as per manufacturer recommendation? Motor needs only conventional cleaning.