Emma this is a dangerous practice as your uv light will not be able to penetrate through the glitter. This will leave uncured gel on the nails, which will lead to overexposure and ultimately a much higher risk of an allergic reaction for your client. Glitter should only be stuck to the sticky top film left on the nails after curing.
The picture show has a high density of glitter because the glitter is very finely milled, if you use craft glitter it will be chunkier so there will be little gaps left and it won't look as dense. Also craft glitter is know to contain allergens like nickel and cobalt chloride and is not suitable for use in nail coatings, again you are leaving you clients open to over exposure.
Use a glitter that is meant for the nails, like Lecente, and pack the glitter on at the cuticle area like you would pack and eyeshadow onto your lid. Then with a very light pressure brush the excess off the nails going side to side at the cuticle to get rid of the bulk of the excess glitter, the from cuticle to free edge when there is hardly any left of the nail, this should fade the glitter nicely for you, also using Lecente glitter means it stays flat on the nail with no bits sticking up so you rarely have to topcoat twice, which means less expense for you, a quicker service and a quicker removal time.
