Brake pads

Hi, I saw the instruction on Mercedes shop regarding the procedure on changing the brake pads. The page is well written in detail and I am going to try to do that myself.
I still have some unknown about the steps..
Why is that important to uncapping the brake-fluid reservoir, and fitting a rag over the top of the fluid reservoir ? which means to open the brake-fuild reservoir, then put a rag over it ? Do I have to also unclip some of other plugs at the brake-fuild reservoir ?
For the brake paste, is that possible to just use other brake pastes, besides the mercedes OE brake paste..
Thank you very much for your time.
And especially to the one who post the procedures.
Peter regards

The OE brake paste is about 75 cents a packet, not to mention most places will give it to you free with the rest of the parts. Why mess with something so inexpensive and important?

The reason you want to cover the fluid reservoir is so that any brake fluid that splashes up goes no further. While the cap normally performs that function you do not want the system fully pressurized. It makes prying back the pistons much easier. By the way, if ANY brake fluid contacts any painted surface the paint is toast!

Just carefully follow the steps we outlined in the DIY article and you should be fine.

Happy Wrenching....Lee

Dear Lee.
Hi, Is Pete again. I went into some obstacles for the brake pad replacement. I couldn't install the new pads to the rear brake clipers. They are thicker, and I can fit them in. When I insert the new pads I tired to push the piston back at the same time as I push the pads in.
I choice the mintexs brake pads from bekkers besides the MB pads. They had sended me a couple of wrong rear pads already. Spended around 120 trying to get the new pads install at the dealer. They had the mintex factory rep call me and claim they this time it should be right.
The mintex brake pads are for the 400, 500, and 600 series. Fron 91 and on.
I am not sure rather they had send me the worng ones again ? ( 300E uses 400E pads ? on the 93 model ? )
Does my rear brake had sensors ? As I don't see any on them insert to the pads ?
I just needed to find out a couple of things, do u think they had send me the worng parts again ? Or I forgot to do certain things, therefore the pads won't go in as it should ?
Thank you very much for your help
Pete regards

I enquired about brake pads on another thread.It seems that the E series uses several types of calipers.I think I shall buy it from the local dealer in Canada where prices have come down 33% in 2 years on brake parts ,thank to our mail order competitors(in case mail order sent me the wrong parts and it's diff to return).Tom