23000+ products with different shipping profile - how to

[GrandArchitect]

Hey guys,

I've stumbled onto a problem. Currently have around 30k products in the store. All these products have a flat shipping profile(SP1).

Recently imported 23000 products that will have a weight based shipping profile(SP2). 

My current issue is, I can't add these products to SP2 via API. Apparently I have to do this by hand, which is out of question.

I have 6 websites, for different regions, with the same products.

I'm good with coding but, didn't find a way to do this via the API. Any suggestion is welcomed.

- trying to stay away from apps due to cost(6x app cost)