Traditionally felt makers use 'tops' which are processed and dyed (if nec.) for immediate use. Here's a tutorial... A guide to basic wet felt making. You can find these in my shop. Merino is usually the 'top' of choice among felt makers.
However, it is entirely possible to use fleece if prepped correctly... I do recommend wearing a good pair of rubber gloves throughout the process until you have dry and clean fleece, as there are certain health issues with handling raw fleece.
Firstly you will need to lay each fleece out on a long table (protect the table with plastic), or if you have a garden the lawn. You will need to ‘skirt’ the edges of the fleece to remove the matted and overly dirty edges (dung mostly). Then you need to ‘sort’ your fleece. This is the process of going over the remaining fleece very carefully to remove grass and other vegetable matter, plus any matted or dug effected areas. Then you are ready for washing.
Washing the fleece will take time and I do recommend buying a large bucket specifically for this purpose. Here are some instructions... Washing fleece. You may need to repeat this process several times depending on how greasy your fleece is. Felt making will require a grease free fleece; otherwise the grease will stop the soap and rubbing action from working.
Once it is dry you should leave the fleece in a container that will allow good air flow, nothing plastic… Fibre care. You will need to prep all of your fleece to begin with, as fleece is best stored without the Lanolin grease.
After this time you can begin carding. As you have so much to process and carding will take a very long time with this amount of fleece I do suggest a Drum carder... The 36 ppi is the one you will need Ashford drum carder. If all of the fleece is prewashed you can card as you go along, keeping the remainder of the fleeces stored ready for later use. Here is where you can start to follow the YouTube videos you saw by me on YouTube.