Exclude interim Location from Sales Order availability

Hi all,

I need to exclude stock in 902 storage type from Sales order availability check.
I have read everything written on "storage location Control" in order to achieve this and understand the theory behind it all.
However, I have some questions about the logistics of actually implementing this approach.

Current setup:
-I have setup SLOC 4001 in plant 1139, WH 102, and ticked "do not copy storage location in TR"
-I have setup SLOC 4000 in plant 1139 WH 102 and defined it as the standard storage location (this is where we GR all our stock receipts at present, and where the availability check looks to)
-I have automatic TO creation in the foreground for 101 MVT
- I do not have cumulative posting changes set

Questions:

1) I have read that the first step is to "set up interim storage area 902 so that the system assigns the stock in this storage type to storage location 4001".
How do I do this? I haven't seen anywhere linking the storage type 902 to the SLOC

2) Is it standard SLOC 4000 that will show in MB51 Material Docs view under MVT 101, or will it be SLOC 4001?

3) Finally, is this something I have to implement across all materials in the WH? I have 2 materials, A and B. WH staff would prefer to keep GR SLOC 4000 for mat A if possible, and I don't mind if mat A in 902 is allocated to sales order. It is stopping Mat B that is the concern

Thank you so much for your help. I will of course << Text Removed >>

Regards,

Ruairi