How to connect ECC to PI for Proxy

Hello All,

We are planning to migrate to PO 7.4 single stack from current PI 7.3 Dual stack.We have many interfaces between ECC and PI using proxy.

And we are migrating in phase wise approach only not bing bang approach.so please can you let me know the answer to following question:

1.How to send proxy data from ecc to both the PI and PO system.
I saw the below link but not able to understand much,can anyone please help me with step by step approach please:

Connect SAP Application System to multiple SAP PI Integration Server - Variant n°1

2.Both my PI and PO will be able to send proxy data to ecc,Or some additional settings are required?

Thanks

Naveen