Firstly, you should ensure all the tools you use are spotlessly clean as any trace of dirt, grit or old plaster will ruin the finish of your wall.
Protect the surrounding areas with dust sheets.
Repair any large cracks.
Clean the wall you are plastering to remove any dust or loose debris. Begin by brushing the wall with a stiff brush and then wipe down with a damp cloth.
Prepare the wall with PVA glue. Mix the PVA one part glue to four parts water and brush or roll this onto the wall.
Once the glue is tacky you can begin to plaster.
Fill a large bucket to the halfway mark with cool, clean water. Pour the plaster into the water and mix. Stir the plaster continuously until it thickens and is smooth and free of lumps. Once the stirrer can stand up on its own in the plaster you have reached the right level of consistency.
Heap plenty of the plaster onto your hawk. Slide the flat edge of the trowel under one end of the plaster and pick up enough plaster to complete a strip from floor to ceiling. Make sure the plaster is sitting in the centre of the trowel.
Hold the trowel at a slight angle to prevent it sucking the plaster back off the wall. Now, starting in the bottom corner, smear the plaster across the wall. You are aiming for a layer of about 1/2″, but you don’t need to apply it precisely at this point as you will be smoothing it down later.
Once you reach the top of the wall slide the trowel along about 2-3 inches and then bring it back down the wall. Continue this process refilling the hawk as necessary and scooping up the plaster into the trowel until the wall is covered.
Once the plaster is in place, you are ready to smooth it. If the plaster has already begun to dry you might need to spray it with clean water to wet it again. Now clear and clean your trowel and run it over the wall in all directions, applying a consistent amount of pressure. Focus on any spots where the plaster is thicker.
Once you have an even first coat you should lightly rake the wall with a notched trowel to give the next layer something to adhere to.
The final layer of plaster, called the skim coat, should be applied in the same way except you are aiming for a depth of around 2 mm.