Coffee stir sticks if it must be real wood.
Color washes can bring out any detail already there that is imperceptible most of the time; "pop". (blk, brwn, grey¿?)
Cheap water based craft acrylics are a good place to start. If you dont like it, wash it off. Cure time has a direct relationship to how quickly each layer of color may wash off. So a mistake removed today doesn't always effect the one before it. But enough dawn & a stiff plastic brush and paint years old is comming off (more so with flats and satins, glosses hang on tighter).
I mostly just save my brushwater for washes, every color pigment within black, similar to real earth and weathering aroun here; milage may vary. Sometimes I brush it on, sometimes I pour it on, literally. Too dark?; water it down. Too light?; add a drop of color. No hurry, no worry.
Windows: Frosted? Scotch tape. Window panes? Carry out salad container, Q-tip box, etc. . Just avoid super glue, the fumes cloud the clear plastics. (the clearest glue for models is "Canopy glue", but not really "needed" here) I have some Scotch tape widows that I added in the early 70s. that still haven't lifted. (two layers stuck together on the pane so the tack layer doesn't collect dust..e.g., a short piece centered on a long one, so the ends can hold it up)
Lighting is always cool. Wait till you run passenger cars in a dark room with some mood music, lol.
I almost hate the thought, but I had a single led lit by 1 D cell for near 4 months. If it was dimmed, it might have been doubled that. If I shut it off on occasion, maybe a year or more. The weight of the battery was nice too. Not for every car, and I hate dead batterys with a passion, never remember to buy them either, but that timeframe is at the back of my mind a lot anyhow.
A pick up shoe can be made from a brass feeler gauge and some isolation. (automotive, etc) They are pretty reliable. So far they perform better on my problem turnouts than some rollers and manufactured shoes do. They also flicker less than rollers... but do have more drag. On one or two cars, I find it very acceptible. 5 or 6 shoes adds up though.
I've also made rollers from bushings, not great though. Pickup relies on a large diameter side thrust connection and it gets iffy. The side pressure makes contact, but also more thrust drag and without the benefit of spring weight for traction at roller, the sides drag can stop the roller from spinning. (normal set ups don't rely on side thrust contact, this uses the axle and an isolated plastic tube cover, within the bushing's center. The (heavy, ball shaped) bushing center just floats very loosely around the axle & tube with a 1/16" -1/8" overize diameter hole, the bushing weight is the only downforce. )
The axle tips shown may be blunt end types. Not a lot to do but change to a needle tip truck or going with cast rollerbearing trucks, etc.. Choosing a pair with rollers only prudent if you do change (& fyi, there are many slight changes in trucks, some more easily noticed than others; look VERY close at heights especially, despite similar appearing sideframes etc.. )
Over time, the stops or sqeezed part of the axles that limits side travel of wheels, can wear flat and drag. They may even let the wheel backs short on pw uncouplers and turnout rails. A small washer there can help with side thrust drag against the stop sometimes. Brass and plastic tubes (stir straws to pen parts) for use as axle tubes is another option (applicable to pickup mounting too)
Polish the axle. Oil the wheel/axle (or use a dry lube like t-9, dries to a thin teflon wax coat). Graphite used sparingly works well, but is too messy for most folk.
"Is it worth it?" is a matter of opinion. Some folk need a store bought fit and finish to be happy, some don't. Know thyself 
Personally I have enough fun building, that the outcome is nearly redundant. Nearly each one becomes a new favorite. The non-favs get used, but might become something else when I'm ready again.
On the cut, I use exacto saws for close cuts, or if I can spare material, dremel wheels (carefully, they can get grabby in plastic) or my bandsaw 
; cutting close, but not on my lines (if possible).
Then I use a big flat file, or sandpaper on glass or plate metal, etc. to remove material till I like the mating seams . Gluing the paper really helps. If the paper isnt secured, it just isn't as flat when sanded (glass is best too) (3m spray glue is ideal for sandpaper imo, lightly so its easily peeled off later)
Backing any seams with plastic scrap adds strength, along with the suggestion for blocks to reinforce 90° joints at the body to car, it will make it a survivor.
