Principally there are two kinds of paints intended for glass that you can utilize. There is water based and non-water based paint.
Hence if you opt to apply the non water based type, you ought to use a ceramic thinner to weaken the paint with. Watch your brushes though as they will have to be cleaned with a thinner, or even white spirit. They take quite a time to dry out, usually perhaps about 2 hours, however to be absolutely dry anything up to 8 hours. so a bit of tolerance is needed.
If you try the water based paints which you do,in actual fact, dilute with water, cleaning will not be much of a problem. Your brushes etc. may dry in roughly 20 minutes, but will not really be properly dry possibly for days.
For your guide lines, on top of glass you want to avail yourself of an outliner, which does just that. At this point you require a firm hand as you press the paint from the tube to produce your lines. You can acquire them in a number of colour shades, nevertheless there are a few main ones one can apply. Namely black, gold, silver, along with a kind of grey.
These are in all probability best if you paint them on initially to mark out your actual pattern, or you might go over a painted surface to add some detail.
When you use the outliner I always squeeze a bit out of the tube to start with in case it is blocked, or has some air bubbles. It is better if you make an effort to keep the top clean as you go along, to stop making awfully thick lines.
You can as well use leading tape. This is by and large used on windows as well as doors. In the main this comes in a couple of widths and on a roll. In this situation the backing wants to be pulled off so that you can affix the tape to the glass and in that case try to curve it to formulate your design.
Glass does need to be prepared first to get rid of any grease from your surface, so that your paint will stick. You can use white spirit for this.
At this time when you do progress to paint within your outlines with your brush, don’t be sparing with the paint! You ought to get a good stained glass effect. If you need a paler colour and you are using a water based paint, weaken it with water.
If, however, it is a non water based paint that you are using, you could use a gloss varnish. You will need to use a palette for your paint. I would not recommend that you go straight from the jar as you will not want your colours to get soiled or watered down.
If you have a large space to cover you could always use a sponge to apply the paint and you could still blend your colours while they are wet.