On brick and on AAC or concrete block, apply gypsum plaster directly. On smooth concrete (Mivan, RCC, precast), roll on a bonding agent first.
Smooth concrete is dense and gives plaster nothing to hold. Gypbond Pro gives it a rough, bonded key: roll on one coat, wait 24 hours, then plaster. You can plaster up to 14 days after coating; after that, roll a fresh coat. One kilo covers up to 60 sq ft.
The wall must be free of dust and oil.