Thanks so much, Moya and Jean!! Very interesting.
I checked again on the Gerstendörfer website (they produce the Kölner and Instacoll products): They say that the Miniatum only works for transfer leaf gold (not for imitation gold, yes, the expression seems to be Schlagmetall, all these words are technical terms that are also new for me

), so that mirrors your experience. They say though that it should be active for 24 hours after it's dry? Confusing.
Also they say that gilding with Miniatum should not be burnished with an agate stone, only with cotton wool or the special tissue they offer, and that equally high gloss can be achieved like that than with the traditional stone polishing / burnishing. Again, not sure about the right terms here!
I post here a link to the company that produces the Kölner and Instacoll products: you can see that they offer the stuff also in smaller bottles which I think is great for trying …
http://www.blattgold.de/Gilding_cat_208.htmlThanks, Jean, for the info about Tressers Gold size. I guess for now I'll order some Instacoll and Miniatum and see how it goes. It is very expensive because of shipping and taxes for me to order supplies from the USA, so I try to find something I can get local

.
I guess I just have to buy a bottle of each and try what I can do with it

.
Also what you describe about combining flat and raised gilding sound very classy!! – But what do you mean you do not have the right burnisher, Jean? You mean such an agate stone? Harvest Crittenden says also to use only cotton wool for a very light polishing … do you mean by folder the bookbinding tool? – Sorry if my questions sound silly, but this is really a new world for me, plus I have to check a lot of words for the English-German translation

.
And one thing more – do you know how to make little ornaments in the gold itself? Do you need such an instrument:
http://www.blattgold.de/Pearl-Ornament-Punches_detail_44_249.htmlor is it possible with something else? Could this be done on a 'raised gilding' with Instacoll?
Another question, am I wrong or isn't traditional gesso for gilding rather poisonous because of the lead white in it? That's at least what I found in a recipe in a German calligraphy forum, that's why I didn't ask about that at all in my original post …
Thanks so much again for your answers.