Q. What is the best way to Spray Near Molten Glass with thermoluster?

A 1991 article by Bryce Lundstrom from Glass Line that describes using Thermoluster Mother of Pearl might be useful to you. The article includes a formula for diluting with swimming pool acid.

Boyce Lundstrom. "Olridizing Pyrex Glass at the Benchö. Glass Line. Feb/Mar 1991. 4.5.

This is a link to an article on iridescent glass technique: 

David Gruenig. "Iridescent Glass Technique." ausglass Magazine. Autumn-Winter 1994. 19-22. Web.

I added our lengthy list of articles relating to irridescent glass. These deal with historical and relatively recent information about methods used to irridize glass (also how to used previously irridized flat glass).

If you wish to obtain copies of items in our list, please contact your local library. The Rakow Research Library is a member of the Online Computer Library Center (OCLC). Your library can contact us through OCLC or they may send an Interlibrary Loan form to us by e-mail. We send copies of articles and will also loan certain books if a second copy is available in the library collection. Books are loaned for a four week period. For further information, please see our web page: https://www.cmog.org/research/library/about/interlibrary-loan

If you are using a brand-name thermoluster, contact the manufacturer (or supplier) for instructions that are specific to their formula. They probably have instructions and a MSDS (material safety data sheets) that specifies safe handling and dilution for the luster. Both contact and the fumes can be dangerous.

Have you tried an internet search? I Googled thermoluster and found several online discussions about techniques.

Good luck with your project. Please let me know if I can help you again.