A couple of nice videos that review The Most Irregular Verbs in the Preterite:
Remember if you want to get the verb forms perfected then repeated practice and drilling is the way to go. Here are plenty more for you to practice with:
Trinity.edu – This is just a link to the main page so you will have to scroll down or ctrl+f and search for ‘Preterite‘. There are loads of drills for you to work with.
Ver-Taal – Again this link will only bring you to a main page but you can scroll or search for the preterite excercises. There are a few to work with.