Stitching on silk gauze is actually a form of petit point, but a person experienced with either form of counted cross stitch should have no trouble stitching on silk gauze (except possibly for vision difficulties).
The fabric is a special silk mesh originally made for the medical profession for the treatment of burn victims. Although several mesh sizes are available, the one most commonly used for stitching is 40-count. This means 40 stitches to the inch, or 1600 stitches to the square inch. The gauze is extremely expensive, at over US$300 (yes, three hundred dollars) per yard. Luckily, a little goes a long way. The gauze sold for stitching may come mounted in a cardboard frame, and is sold in sizes such as 5"x7". Keep the gauze in the frame while stitching, and remove it after you are done.
The thread used for stitching may be cotton floss or silk. Use one strand of thread. It does not need to be very long--probably 10" or so.
The needle should be small and sharp, such as a small crewel needle.
The chart may be just about any counted cross stitch chart. Keep in mind that you will not be able to do any quarter stitches. Also, any additions such as beads will be too big. Note that we follow the counted cross stitch tradition rather than the needlepoint when it comes to filling in the background--we do not fill in the background unless the chart calls for it. The gauze is allowed to show.
The stitch is a continental stitch rather than a cross stitch. This looks like a half-stitch from in front, but the back is a long diagonal. For this diagram, come up at the odd numbers and down at the even:
Do not carry thread across the back in an area that will not be stitched. It will show through.
If you have trouble seeing the work area (and most people will), use a magnifying lamp and hold the gauze over a dark background.
This is a way to do counted stitch needlework on non-evenweave fabrics. Waste canvas is a special type of evenweave fabric which comes in a variety of mesh sizes. The fabric is unusual in that its threads are held in place with starch. The waste canvas is used by basting it onto a non-evenweave fabric, such as the front of a sweatshirt. This provides a grid for doing counted cross stitch or other counted thread stitches. Once the stitching is complete, the waste canvas is removed by dampening the canvas to remove the starch which binds its threads together. These threads are then removed one at a time, with tweezers.