Line breeding/inbreeding is generally acceptable and a common practice in reptile breeding.
You don't see the same negative effects as you do in mammalian breeding. But it's always good to outcross with that being said.
In order to prove out morphs or recessive genes, the fastest and easiest way would be line breeding (mother - son/father - daughter).
Many multi gened sons replace their single gened fathers as breeding studs.
You also have to be conscious of what you're breeding too. If you hatch out a kinked offspring, it would be safe to assume he wouldn't be good breeding material in case it was a heritable defect. So breeding healthy quality specimens is the key.
Overall, it would be safe to line breed a few generations before bringing in new blood.
Like you mentioned, that's how Brian Gundy's Gold Blush came around; selective line breeding.