u usually use just old style soap (i try to get antique bars where I can) and water at first, if you don't make the rubbing cloth too wet it will work fine getting all the gunk, grime and other out of the covering of the case
and that's step one
I'm an antiquarian book restorer although I perform another trade these days due to disability so I know my coverings and case finishes
step 2
the case is now clean and dry and since there's wood beneath the covering needs to be checked for loose ends if there are any the ends need to be damped and the (acid-free bookbinders) glue needs to be applied to the wood and if there are hollow bids of covering next to the loose ends use a spatula to push in the glue as far as possible then wait until the glue is tacky then rub and stretch a bit on the loose end sides usually the corners then when half dry clamp with boards
step 3
the now cleaned and reattached cover will have scuffs, scratches and even holes (sometimes) for this I make my own filler from beeswax and coloring (if you don't have such skills use crayons) and I start to fill in the damage bit by bit and its apply and then rub and repeat that process until all seem to be fully filled in
step 4 now you have a case with rather bright spots of color that are brighter than the base color not to worry because were at the finishing point well I make my own rubbing wax to match exactly the color a book or a gramophone needs to be the clue in case of books can be found on the inside of the cover the part that was not exposed to light the same goes for portable gramophones the interior in a lot of cases is untouched by mother sun so we know the color
when we have the right type of wax/color mix of wax or,.. the right color shoe wax we can apply and the end result will be a good almost as-new finish but with a touch of age just as we like it its a well preserved antique instead of a battered piece!
but will I be able to make something of this!! my newest prize!
it was found in Tanzania 20 years ago and it had been intensively used for decades!
tino