You need Kaizen foam, very easy to cut as it comes in layers:
Pick and pluck foam is garbage plus it attracts lots of moisture (over time) because it is a huge sponge, kaizen foam is not a sponge and if it gets wet, water will not soak into the material.
You can buy the Kaizen foam from the pelican store for $50 plus shipping (another $50) for an already 1500 case sized piece, or you can go to Home Depot and order a huge piece for less but not sure which thickness they have (this is important).
I bought it from the pelican store and it fits the case perfectly, it comes in two pieces which means it allows me to create 2 different 'levels'; the top level (the one you see when you open the case) has the holster and pouches and other accessories, lower level (hidden) contains 2 pistols and 6 magazines.
Cheers.