Hello there, I know that my bid is out of your project budget, but please make time and read my bid.
I have an custom extension for product options, and you can add options by category. So you can select shoes category and add sizes for all products in shoes category, instead of going one by one products and add size to each one.
Let me know which extension are you using for export/import products, I am available to help you.
Best Regards,
Bojan