It is important to clean up the tyre surface with the scraper to remove any built-up rubber. This will allow GRIP to penetrate more evenly throughout the tyre surface and also helps to prepare the tyre for the next race.
Pour some GRIP into the container and then brush on to the tyre's tread surface - there is no benefit in applying it to the sidewall. The first coat will probably take 20-30 minutes to absorb, depending on room temperature. Further coats of GRIP can then be applied as desired, leaving similar absorption time after each coat. Four or five additional coats will give a significant increase in adhesion (durometer reading about 10-15 points lower).