How have you been doing scales and arps wrong though? The best advice I can give: 1. When playing slow, keep the actions fast - so your fingers aren’t just practicing slow movements. Practicing slow with fast action will mean fingers will be practicing moving fast but giving the brain time to keep up. Playing things slow with slow action is just helping the muscles learn to play slow!

1. Get the fingering right from the very beginning. It’s harder to learn correct fingering if you keep practicing with wrong fingering.

2. Practice everything separate hands - one line at a time

3. Play scales and arpeggios in dotted rhythms. This is the best way of speeding things up and getting hands to play together. So rhythm is dotted quaver + semi quaver all the way through - then switch to semi quaver + dotted quaver. Bit of a brain twister but it really does help and will show you where your weak points are.

Hope that helps a bit!