I just take a cheap tooth brush, that my kids got at school, when teh dentist was in class to brush off the crud and then take some long, single sided Q-tipps you normally use to clean electronic devices. Since these mostly have wooden shafts on them, you can also use the cotton free side to get into corners and scrape out the dirt.
Advantage on the long q-tipp is, that you can put some cleaning solvent or gun oil onto the cotton tipp and get nearly everywhere you have to. And since there is no metall on them, you can`t scratch the finish.
Just like whith the pipe cleaners, you can really nicely clean the rails on the frame and slide.
Also, since the cotton is normally white, you can always see, if there is still some dirt on the cleaned area or not.