Fire polishing in a mould
You CAN do this. People do it from time to time. you need to think about what you want to achieve. If you want to polish the edges, do it by cold working – Paul has a nice book on cold working availavble from this site.
If you want to polish the surface after, for example, sandblasting then you do need to consider fire polishing in the mould. Make sure you have the mould covered with kiln wash, so you do not get any sticking. Please note: you will also have to clean and re-coat the mould after the fire polishing session, as the chemical composition changes after being in or above the fire polishing temperature causing it to stick to the glass on the next firing.
Use the usual slump scheule up to about 600C and then fire fast to the fire polish temperature with a minimum soak – observation is a good idea to be able to tell when the piece has become glossy. This proceedure will not always work = the piece may slump further, making it unsuitable; It may slump to one side; it may move to the bottom; it may stick to the mould.
I think it is a good idea to know if you need to fire polish at all. You can polish glass by hand with more assurance of success.