Split install.wim into max size 320mb chunks. I used wimlib to do the splitting, there are several ways to do it - you could use microsofts dism.
The usual way:
The first cd is bootable and contains the installation media as usual - except sources install.wim is replaced by the first chunk , install.swm.
Second cd - not bootable - contains a folder called sources with install2.swm
Third cd - not bootable - contains a folder called sources with install3.swm
and so on. That uses a lot of cds.
Cheating way:
I cheated to reduce the number of cds by doing this:
CD1
CD1 sources folder contains install.swm instead of install.wim
CD2 only a folder called sources
Which contains only install2.swm AND install3.swm
CD3 contains a folder called sources with install4.swm AND install5.swm
and so on.
If you cheat like I did, it reduces the number of cds needed to 5. You have to pay attention, because after inserting cd 2, it copies install2.swm and install3.swm. So it then asks for cd4, because it knows it needs install4.swm - which it thinks is on cd4. But if you cheated, of course you need to insert cd3.