In order to generate the post, convert the latex file into html. This option works much better than converting it into Markdown format first, and also gives more flexibility.

Use pandoc:

pandoc main.tex -o main.html -f latex -t html --mathjax --bibliography sources.bib

After that, complete the file bu running

post -i /path/to/main.html

This will create main.html in the directory from which you run post.

Then, simply copy the content into the Markdown post file.