ExtendScript CS5 - Bridge - Exporting JPEGs as 300DPI from PSDs

I know that Bridge has an Export menu that can be used to convert PSDs to JPEG and then convert them, but I can't figure out how to get access to these functions through the ExtendScript API.

I basically have an array of Thumbnail objects that I need to iterate through and export out 300 DPI JPEGs as I go.

Any ideas? I've already read through the manuals and didn't find anything of use.

My current relevant line looks like: bm.exportTo(new File(exportFilePath),100);