Hi, you would need a competent lab to conduct the migration testing and they would also help you to establish the range of testing required so that it covered all possible types of products and end uses of your customers.
For example some customers may have acidic products, others oily, some may hot fill, some may cold fill and cook or pasteurize. First you need to gather information and understand your current customers products and processes and then work with the lab for what may reasonable be expected to occur.
Once complete whenever you get a new customer or existing customer with a new product you can ask them about their product and processes and specify the most suitable product from your portfolio based on the usual criteria such as price, functionality, aesthetics etc. plus what is best from a migration point of view.
If a customer comes along and say's I'm hot filling at 100C and boiling for an hour and this is outside what you have tested for then you tell the customer what the material is tested to and tell them they need to conduct their own end product testing.
You need a competent lab that specializes in migration testing.
Hope this helps.
By the way if you have a lot of products it can become costly. Oh and you must ensure that you are not introducing any chemical contamination during your manufacturing process such as inks, processing aids, cleaning chemicals etc.