The book by FY Wang mentioned by Kobo-Daishi is the best I know of. It gives, for example, in lesson 1, 32 characters with the regular kai3shu1 next to two examples of semi-cursive xing2shu1 structure, then 20 example sentences for you to practice reading and copying. The characters which have not yet been introduced in semi-cursive are written in regular script, which is nice. Also, the author does a good job of starting with the most basic and common characters, and also of showing in the notes how cursive elements can represent different characters or components thereof. Appendix II also compares cursive forms easily confused. I do recommend this book, but if you're interested in having really beautiful handwriting, you might also consider attending a calligraphy class, first learning kai with a brush, and then xing. As for real cao3shu1, it is often too hard even for native speakers to read, and never really moved beyond use by the literati artists. You could study it later if interested, but that would be the last step and you won't really need it.