I have never used such but found this info in a forum " The conformature was just to measure the head, when ANY custom made hat was ordered by the customer. They kept the "punch card" of your head on file for future orders. The conformature is worthless other than a nice museum piece without the other half, the "formateur". This is the part that goes inside the hat when it is given it's final flanging and sizing. Hence it will supposedly fit your specific head shape.
The "self conforming" hats, like RESISTOL, were designed with qality leather sweat and felt that was supple enough to "conform" to your head. Obviously your has size would be the same, just the quality of materials would allow the hat to more closely "conform" to your head after a few days of wearing it."
Another member has been searching for the same http://hatacademy.com/forum/topics/hat-conformateur Hopefully someone here has used such and can assist.
One day, i hope to own one of these creations. Alas they are rare and very expensive.
For a milliner, there would be very very little need for this as most hats are made soft and fairly flexible. thus would mould to pretty much any shape head in the hats size. An exception may be if a client has a very unusual shaped cranium. A large set of calipers will measure length and width of a head, and with circumference will tell you if they have a wide, regular or narrow head that may need to be taken into account.
The conformature was more important in men's hat making, particularly in regard to top hats and bowlers which are a very stiff and rigid. The client would buy the hat and then the hat would be adjusted to their particular head shape otherwise it would put unbearable pressure on points of the head such as temples or forehead.
For fedora type hats, again, softer and more flexible thus not so important.
There is a very expensive brand new one available for around $5000 + (USD) and some cheap blue plastic ones around from the USA also. (google will find them)
I have been working on a prototype conformature for some time