I have played with gilding over 35 years as part of doing decoratuve object creation. In amother life I used to restore carrousel art for about 8 years. That was over wooden animals - mosttly basswood which is great fpr carving. There was base paint build up - tyically catalyzed automotive enamels and then the quick dry varnishes which creat a great tack surface. Fine leafing metals like Manetti literally waft /float away in a gentle breeze and stick to anything with the most minor amount of oil or gelatin. There are very thinn long hair brushes about 4"wide to use static electricity to pick up and place leaf where you want it. The reddish hue seen peaking thru surface gilding is a spoft substrate cslled Hastings Clay. It allows a burnishing tool to bring up a high polish.
My true love in gilding was water gilding (tiny bit of gelatin in a solution of water) on reverse side of glass. It is reverse paint or eglomisé. Attached are some images of piece - a trifold screen I created. I did mine with a filagree positive and negative effect. It ends up being partially mirrored. The gilding dances light in every direction.
This particular folding screen was created with extremely detailed silk screens. The green was a formulation of translucent nazdar inks that were layered to build variations in the green. Then each panel was coated with gelatinized water. After that a white gold leaf was carefully applied to the whole pane making a mirror. After that, another pass of green design on the back. That masked the areas that would remain mirrored. Then, I very carefully scrubbed to remove the leaf in between the masked / print over areas. It took alot of time with a Qtip and light abrasive. Then another pass of green screened to protect the edges with a .03" halo of ink.
It is labor intensive and takes considerable care, but the results make it rewarding. Its kind of an all or nothing endeavor.
The other piece is an antique La Forné coal hod, mid Victorian circa 1860-70. It has some surface gilding in borders that has deteriorated over the years. It also has a striking heraldic snowflake design that is reverse painted & gilded glass. I've been acquiring eglomisé pieces for years.