Sound-wise.
A friendly & business-like approach is the way I've always looked at it. Excepting & making a trade is a contract and should be treated that way.
It's easy to get overwhelmed with many trades. Just take them one at a time.
What I do is once it is at the exact stage. I pull the cards, get them ready to mail and go to the next one. Sometimes I send a few trade proposals, then within the same amount of time "within a few days" get a few trade offers. I will message them on their PM, not on the trade offer. Then tell them I saw the trade offer. I've got a few ahead of you and will get to it in a few days. This lets them know what is up and takes the heat off you when you have many at once. This is where the friendly communication come in. The pulling cards, packaging them and posting them. Clicking the update is the business side. Alone with messaging the tracking # or stating they are coming in a PWE. Keeping it simple and doing one at a time, is a key to making it easy. Then before you know it your active trades are a list that will always be there.
And just like the outgoing cards get on them incoming cards, don't let them sit around and pile up. Get them checked against the proposal and marked reserved & then completed. You can always put off putting them away where they belong till you get a few. It's what I do. When the stack is around 40 or 50 cards. It's time to put them where they belong.
YOU CAN PULL THAT OFF.
What is that behind you!?! Oh, It's me! Looking at the cards you have, That I want. :)