There are different ways to apply a drawing to the glass. You can do this using mechanical devices (sandblasting machine, engraver) or using hydrofluoric acid and various pastes, fluids based on it.
Master uses pasta Armor etch. Still need a stencil you can buy, but you can cut it yourself) and a brush.
Before etching, be sure to thoroughly wash the glass. Hydrofluoric acid corrodes glass, but fat, oil is an obstacle for it. It is not advisable to even touch the treatment site.
A stencil is glued onto clean glass and the composition is applied.
The pickling composition used by the master must be kept for a minute. After a minute, carefully remove the stencil, etching compound and wash the glass. You should get a drawing.
Please note that pickling compounds are available for thick and thin glass.