Using a paint bucket is an ideal way to mix, store and dispense your wallpaper paste.
It enables you to use a paint roller to apply your paste to the paper and wall. This is a quicker process than using a brush and is easier to get an even coverage on both walls when sizing and paper.
To go with the bucket use a pile roller sleeve and an old brush to get paste into any awkward areas.
It is possible to use paste over a period of a few days but do watch that it does not start to become mouldy. This will be carried over to the wall wallpaper resulting in discoloured paper in months to come.