Keep the chords nice and short in the A section by relaxing your fretting hand quickly and evenly after each strum.
Try to get the palm mutes slides and vibrato in the right places in the B section (above)
The videos below are from the tracks Fallout and Indecisive. each section has been recorded at a slightly slower speed than required in the exam, to allow you to concentrate on getting both right and left hand parts correct. Most of these videos will loop automatically to allow repeated attempts without reaching for your mouse. Playing them through a media player such as VLC (see link on IT page) will enable you to slow them down further if necessary.
In the C section of Indecisive (above), Rock School advise alternate strumming (down up) try to strike both strings with every stroke and don't forget the tempo in the videos is about 15% slower than you need for your exam!
Keep your finger flat on the fretboard and keep the pressure on as you slide up to the 3rd fret. Keep the last three chords nice and short as indicated by the staccato dots above the notes in the music.