Get the Leaving Cert Engineering book from Brighter Minds, and as well as the book you'll access to a full range of videos and quizzes which cover every aspect of the course. The longest video is less than 15 minutes long, so it's a very time efficient way of covering the course. The website is www.brighterminds.ie.
i didnt really do use the book, it just so happens that i enjoy watching alot of machining and engineering related youtube channels, so most of my knowledge came from there. but one big thing that helps is doing the past pepars, and use the marking scheme to your advantage, you can learn the exact words or facts that the examiner wants to see and that changes very little from year to year. but if you want to go through the book the designated welding, material testing and machining chapters ect are pretty nice. and with regards to your project, try fit some 3d printed shit in there, examiners love it. mine had to be like 30% 3d printed at least by the time i finished.