Canna, you can mix the castings right into soil mix. I'm about 15% castings by volume in my mix but less is fine. More might be overkill.
Lots of people like them for tea as you know. I don't mess with teas figuring that I can feed the microbes directly in the soil and they will thrive just fine. For top dressing I mix them with an equal amount of new soil and a handful of Yum-Yum. If you make the mix a day or two ahead and make it slightly damp it will get very bioactive. Then I scratch the mix into the top couple of inches of soil and water it in.
Thanks PeeJay. I'll mix some into the soil in the bin.
When winter sets in I won't be able to get the castings outdoors, so I figure it will be good to use the "tea" that I will get from the indoor bin. I've always wanted to try the teas, and I have a bubbler that can keep them from going anaerobic on me if not used immediately.
Your plants are looking awesome and I can't wait for the seeds to begin!