I've been at one; it's just like consecrating a new church.
Same here. In the Greek & Antiochian Orthodox Churches in Australia , a purchased Church building is treated like any new Church building, and receives it's Consecration and Chrisimation from the Bishop. The Cathedral Church of Archbishop Stylianos (GO Australia), is a converted, sandstone Anglican Church dating back to the convict era.
I think some communities have just done a blessing of the building (holy water) before using it.
In Australia, the Sanctification of Holy Water is used prior to the Liturgy only when the building is shared.
For example, a PanOrthodox Liturgy takes place annually in the Olympic Stadium in Sydney which is preceded with a Sanctification of Holy Water service.