i used inletting black once .
IMO it’s whats called a fools buy . IE you buy something that does the very same thing as something cheaper or free because a book or list of required items says to .
Candle or lamp black works good but its messy and can get all over everything .
Here is what I do . Go down to the store and get you a larger black Permanent , Marks a Lot , marker .
The one with about a half inch head used for posters and such . They work great for coating a barrel flat as well as the inside of lock plats . Sharpies will do the same thing . Just get one with a big enough tip so as you can color things quickly .
Markers will transfer usually 2 to 3 times before you have to re coat the area . They also will not bleed gunk all over everything . They also do not leave an oil on the wood that must be removed .
For my inletting , that all I use anymore