Although popular, it’s best to stay away from cardboard scrapers as they tend to soak or absorb the liquid portion of the inks. Some screen supply stores offer specially designed plastic ink scrapers. These plastic scrapers feature rounded corners so they avoid harming the screens.
As far as the cleaning liquids go, there are many available that do a great job. You can usually use an ink degradant on the screen to help break down the ink chemistry. However, they seem to be greasy in nature, so once you have cleaned the screen with a degradant, it may be difficult to get tapes to stick to the screen. It is often necessary to add a final cleaning using a more aggressive solvent to achieve a clean, dry screen.