I'll look for the link to our International shipping team.
But, basically, you need to have weighed everything (perhaps put the weight in your description when you list it) and then add (in your mnd, the wight of the box/packaging. I use poly mailers because boxes weigh 6 oz to 2-1/2 pounds.
I set my shipping profiles by weight, since international First Class will go from 16 oz to 48 oz, in 4 oz increments. You might just do it in 8oz increments, to even it out - lose some., gain some.
But by the weights, I can always adjust the profiles when the rates go up.
Once you have your rates set, you can go through and set each item by batch shipping -- if you know how much each must weigh.
But you'll have to reset the shipping for each one. Changing what a profile is will not change on existing items, just newly added ones, or ones changed in batch Shipping.
Here's the Team -- GoTo's blog has up-to-date rates. Read my "quickie" for an overview on how to set the rates/zones: