Start with nearby keys
After C major, practice G major and F major. They introduce one accidental each, which is enough slide work without overwhelming the layout.
C major: no sharps or flatsG major: F#F major: Bb
Think pitch first, hole second
A scale is a sequence of pitches. Use the chart to locate each pitch, then let the hole and breath direction become automatic through repetition.
Avoid speed before navigation
If you miss a hole, slow down. Major scale practice should make the map clearer, not train panic movement.