Feedback on Workflow for inventory sales with regards to serial numbers

I would like to get feedback from other users of Manager as to how they manage their workflow for sales of inventory in terms of serial numbers and also to ask about bar code scanner apps for phones as I need to buy a new phone and this is one of the features that I will be looking at.

Customer asks for for quote
I supply quote
They accept
In theory, I should create a sales order, but am waiting on the open/closed status functionality to be brought in for quotes and sales and purchase orders as the desired functionality is to have nothing in sales order if there are no open orders. Currently what I am doing is flaggind the email with acceptance of quote to keep track of their PO number.
Then next step would be for me to create purchase invoice (if buying immediately) and receive goods.
My next step in the future, will be to use phone to scan the serial numbers into excel and import into my helpdesk
Then import/copy the serial numbers into delivery note for the clients for when receiving the goods as they need to record the goods received onto their own inventory system.
Then copy the serial numbers into sales invoice so that the clients have serial numbers on their invoice as well, although I could just rely on my helpdesk which will have serial number, where equipment is installed, date, purchase price and warranty etc.

The problems that I am seeing is that there is no way to import into despatch note or sales invoice, although I could copy the serial numbers. Secondly, no way to link with purchase invoice in event that I need to return a device to a supplier.

What do other people do with regards to workflow for serial numbers as I am finding that I am not keeping up to date with tracking serial numbers from suppliers or to clients (other than the helpdesk) - I think largely because I don’t have a bar code reader in place, but also because there is no serial number import functionality for Manager.

I am also wondering if the optimal route is to create a custom column for serial numbers and use that if only selling one of the product otherwise use the paragraph field if selling say 30 ipads.

Lastly, can anyone recommend a bar code reader app for phones as I don’t need a dedicated scanner for my business - the phone app would be sufficient.