Edit HRMP opening info

docs/build/build-hrmp-channels.md

@@ -30,17 +30,26 @@ the Relay Chain.
 
 ## Opening HRMP Channels with System Parachains
 
-Opening an HRMP channel with a system parachain requires a referendum. Like all other governance
-proposals, proposers should follow best practices like opening a discussion on
+Opening an HRMP channel with a system parachain requires an
+[OpenGov referendum](../learn/learn-guides-polkadot-opengov.md) using the
+[General Admin Track](../learn/learn-polkadot-opengov-origins.md#general-admin). Like all other
+governance proposals, proposers should follow best practices like opening a discussion on
 [Polkassembly](https://polkadot.polkassembly.io/) or [Subsquare](https://polkadot.subsquare.io/) and
 then submitting the proposal on-chain.
 
+Before submitting the proposal, both the system parachain's and the parachain's sovereign accounts
+(both [system accounts](../learn/learn-account-advanced.md#system-accounts)) must have the channel
+deposit of 20 DOT plus the
+[existential deposit](../learn/learn-accounts.md#existential-deposit-and-reaping) and some extra
+funds to cover for fees. Anyone can send those funds via `balances.transferKeepAlive` call to the
+system parachain's sovereign account (if funds are not already available). System parachains have ID
+< 2000 and they can be found on
+[Subscan](https://polkadot.subscan.io/parachain_list?page=2&status=parachain).
+
 Proposals should generally be a `batch_all` call containing:
 
-1. A `force_transfer` of the channel deposit from the Treasury to the System parachain's sovereign
-   account. Remember that a bi-direction channel is _two_ channels so will need double the amount.
 1. A `force_open_hrmp_channel` from your chain to the system chain.
-1. A `force_open_hrmp_channel` from the system chain to your chain.
+2. A `force_open_hrmp_channel` from the system chain to your chain.
 
 :::caution
 
@@ -67,7 +76,6 @@ the community to review and ultimately vote on:
 3.  Technical details of the proposal, including proposal parameters and technical details of this
     call (On Kusama, most proposals were designed as a batchAll calls):
 
-    - A `forceTransfer` of 20 DOT from the Treasury to AssetHub sovereign account.
     - A `forceOpenhrmpchannel` from AssetHub (1,000) to ParaID.
     - A `forceOpenhrmpChannel` from ParaID to AssetHub (1,000).