Hi Malcolm
If you do not have too many finials to do, why not consider doing them in real gold leaf.
It is not that difficult
For outside work, rub the finials down really well to make sure they have no flakey paint or rust. Give the finials a coat of red oxide, allow to dry for at least 24 to 48 hours then rub down with a fine 240 paper.
The gold leaf sheets come in a little pack, like a very thin small book with one sheet of gold between each page, around 24 pages a book. Each gold sheet being about two and a half inches square. The gold sheets come in different colour shades. Price on the internet varies from around £5 to 12 or 14. ( Check how many sheets you get ) You will also need some gold size glue, I think this is around the same price as the leaf but you will only need one pot or bottle.
Check on the pot how long the gold size glue needs to dry before applying the gold sheets. WARNING !! You can not pick off the sheets with your fingers, it will stick to them and make you look like Ggoldfinger!
Use a very very soft, half inch artist brush, to just catch the gold sheet with the bristle ends from the page, then lift it and apply to the finial, anywhere will do, don't bother with being too aaccurate then keep adding sheets all over the finial using the brush to dab all the leaf into the nooks and crannies. The gold will stick to the size, so use up all the bits of leaf even the small bits as you go.
Don't do it on a windy day as the gold leaf is so fine it will just blow away. You may also end up with bits of gold leaf in your hair and over your face. This effect is quite normal!!!
It will last on the finial for many years however it is usually the under surface that goes first, not the gold!!
I guess if you allow 24 sheets per finial that might just do it, say all in at £15 per finial, plus your time of course.
As a very cheap alternative, rub down, coat of red oxide, oil based undercoat, then paint with gold paint from the DIY store.
I know which method I would use!