Heres a tip for planting stuff out thats been grown in reusable pots.
Dig hole and add OM as required.
Take pot same size as the plant is growing in (or the plants pot itself if no others).
Place the pot in the hole at the right depth and backfill around it.
To water BENEATH the plant fill the pot up a few times and allow to drain.
If underplant watering is not required, take the plant out of its pot and take the pot out if the hole.
Take care not to disturb the soil around the hole.
Then place the plant into the hole, firm and water in.
A similar method may be used for potting on plants into a larger pot. Simply use a pot of the same size as the plant is currently gowing in, as a mould for the compost in the new pot.
I have used theis method with some sucess for some while now. It is less sucessfull when planting out recently potted specimens or those that are very pot bound and need teasing out.