Thin coatings are not very effective as thermal barriers. Even a material with a low thermal conductivity will let the substrate heat up after a few seconds of exposure. Thin coatings are sometimes used with actively cooled substrates, but the usual method is to put on a thermal blanket of material such as Min-K or Hi Temp's Micro-porous. This usually has to be a significant fraction of an inch thick, though (at least a tenth).
Hi Temp do have some layered material options but these usually need a certain volume of air in them.
A thinner layer of Min-K might help.
What are your constraints on thickness? What physical assaults might this have (air velocity, particulates)?
A PI or PETI (phenylethynyl-terminated imide) are the 'usual' high temperature resin options. 450°C is very high, though. I'm not at all sure that the Neximid MHT-R you link to is quite adequate. The only 'polymer' I've ever seen that might apply is a silicon-based material and I saw that in 2005. What little info I have is attached.
NB: if using a PI make sure it's not like PMR-15 with carcinogenic MDA (methylenedianiline) in it.