Uniform coating on sharp-corner grooves of superconducting electromagnet

We are in the process of designing a superconducting electromagnet and are exploring options for applying a non-conducting finish to the steel core. The core is all steel with grooves machined into it to contain the windings. The groove dimension is roughly 4 mm by 4 mm with squared edges at the base. Is there a process or a coating that can be applied to the machined surface that will not build up in the corners and be applied with a minimal uniform thickness to prevent the conductor from coming into contact with the steel core? Also, the core is cooled to liquid helium temperature (4.2K) and ideally the coating would be a good thermal conductor.

Thanks in advance!
Matt

The PARYLENE range of coatings is widely used in the electronics industry as an extremely thin moisture and dielectric barrier. It is applied by vapour deposition which could be a problem in your grooves.
Also worth investigating is electrophoretic lacquer. This should give an even coating in the recesses. It is extremely tough but I have no knowledge if the dielectric properties although I would expect it to be a good insulator.