There's a fine line between challenging them so that they can move on up a level and trashing their confidence. I feel sure you'll both face every glitch and backward step as a "learning experience" on that learning curve. That's all you can do, to be honest.
When they attempt Walsh or SD, you can take one of several approaches - you can
1. forewarn them that they may well find it a little difficult, perhaps a little different to what they've been used to. Or
2. you can let them get on with it and after, if it's been a little "floptastic", you can heap praise on them, telling them how proud you are because everyone finds these really hard and they've done well.
Whether you choose 1 or 2, or another option, as long as you praise them to the moon and back, no matter what the outcome, then it's all good
I can vividly remember DD2 looking and feeling like she'd conquered Everest, when she survived a notoriously hard paper
In a way, the mark was irrelevant; her confidence grew because she'd attempted it
You still have time - please try not to worry - it will
all come together. Speed is something that will certainly improve
a) with practice and
b) a good set of sound exam technique skills.
No-one has to slavishly follow their tutor, especially if they have the time and wherewithal to supplement that tuition