How do you clean dirty brass fittings?

Brush away loose dust with a soft bristle brush. You can wipe the metal with a damp cotton cloth, then dry it straight away. Never apply harsh liquid brass cleaners. The chemicals seep into the surrounding timber and leave a white residue that stains the wood.

I was wondering if there is any way to figure out what type of wood my miniature chest of drawers is made of because it looks quite dark but I am not sure if it is mahogany.

Check the grain pattern in a strong light. Mahogany has a relatively straight, open grain with tiny dark flecks. Walnut shows more swirling figures and often fades to a softer brown over time. Turn it around to look at the unpolished backboards. Secondary woods like pine or oak are much easier to identify without a dark surface stain getting in the way.

Can missing veneer be replaced?

Yes. A restorer can splice in matching antique veneer salvaged from ruined furniture. Colour matching the patch to the faded surface takes patience.

My grandmother left me a miniature wardrobe and I noticed the doors are quite warped so they do not close properly anymore, is it possible to flatten them out again?

Wood warps when one side loses or absorbs moisture faster than the other. Cabinetmakers can sometimes coax a door flat again by applying controlled heat and dampness. They clamp the timber between heavy flat boards for several weeks. It works well on solid wood but poses risks to delicate veneers.