I found the vellum Glue Dots difficult and expensive. BTW, it's not like a normal Glue Dot--more like a rub on. It's not very tacky so you have to use a lot of it to make things stick (expensive) and it it's hard to see where you've applied it and where on the sheet there's more to put. Plus it takes a wee bit to apply it.
I really like sprays--Creative Imagination Scrapper's Spray is my fav. Totally invisible, quick and easy and lasts forever so it's fast and economical.
For lots more vellum tips and tricks and other printing stuff, visit my blog.