Real gold is stuck in a small cup with gold foil, and the brush is dipped in the small cup when it is used. Chemical gold is a 25ml vial. If it is too sticky when used, it can be diluted with high-alcohol liquor or medical alcohol.
Gold powder for writing couplets can be bought in the market, and 1000 mesh can be bought. Mix with varnish and dilute with gasoline. Or mix it with white sugar and wine.
However, during the Spring Festival, there may be shops selling ready-made ones. ...