Jars, eyeglasses, drinking glasses, window glass, glass vases, etc. are amongst the most challenging things to paint. One needs to paint the transparency AND the solidity of the object.
Don't worry about painting "glass" itself.
Glass has a tendency to distort objects which are are placed inside.. therefore focus your attention in painting on the distorted shapes "Inside" the glass.
Forget the "shoulds" and paint exactly what you "see" (which is distortion and NOT a clear, sharp, item) by activating the right side of the brain.
Glazing with acrylics when painting glass allows you to capture subtle shades and hues that you see as "reflections".
Glazing mixtures are created using watered down or medium diluted colors. Whites and blacks will be very important when painting glass....as well as many different "shades" of grey. Grey/green, Grey/blue,
etc. Greys are best created using colors rather than one that is sold as black....ie: Ebony black, Mars black, Lamp Black etc.
I really find success in using a product called Liquid Shadow which was developed by a very talented artist (Kerry Trout). Colors can be added to this medium to heighten a color within this medium; which is a fantastic tool. (In a past blog post I have provided information on how to do this effectively). This product can also be thinned even more using a glazing medium. I reach for this product many times when I am painting. This is a product which WORKS....and works well.