Almost any surface will work better if it is primed sealed first, especially for papier mache masks. That can mean texturing (various methods), applying gesso, making sure the surface is sealed before applying paint (enamel or acrylic), and the finishing with various acrylic, latex, varathane.....they all have their own requirements that are usually printed on the instructions of the container they come in.
For instance.....you never want to apply lacuer onto an enamel surface! Some things are more compatible than others. So, you need to make some decisions about which material you will use. There is no universal rule......such as the one you said you saw that instructed to use lacquer to finish surface. If you're trying something new, always do a test piece to make sure it'll work. If you're not sure of the compatibility of various materials.........do a test piece first.
An easy way to attach velcro to masks, without using hot glue, is to use a combination of rubber cement (such as used for leather work) and small rivets (also used for leather work). That works very well. You can also stitch the velcro to the surface, again using some waxed linen thread and leather needle. All these materials would be available in most leather crafting shops.
Gold leaf can be applied to almost any surface.....rough or smooth, depending on what the artist wants. In either case.....you need to seal and prime the surface first, before applying the gold leafing compound.......and then be sure to seal the applied gold leaf with a varnish of some kind, to keep the moisture from getting to it and changing the color.
Good luck. Juanita