No bags are needed. Pumps have a solids rating that is usually in inches which will help you determine the required mill size.
As far as pumps 4 options come to mind positive pressure, a large 1-2” AODD, slurry pump, or centrifugal pump used in beverage transfer (ideally high pulp so fruit juice or beer) all of course need to be appropriately rated. Make sure the AODD pump is groundable and ground the fucker for sure to avoid💥 chill your solvent by inline exchangers or a jacket holding vessel with its own process chiller. Fill at the end of each day and it will be ready in the morning. Just size it to the volume required daily. You can use heat exchangers to help reach final temp as it travels to the extraction chamber if needed. Once your vessel is at temp add your source material and wait until it reaches your extraction temp before adding solvent. Once everything is at temp add solvent and agitate. When done open bottom valve then turn on pump and centrifuge. You can try different micron filter bags in your centrifuge. Ideally Id aim for 20-25 micron bag to also utilize solvent separation as my stage 1 of filtering. You’ll have to balance the micron size with speed and total ethanol recovered vs lost (it may be more economical to go 75 or 100 microns from a time/recovery vs filtration stance).
To upgrade this system get a jacketed centrifuge and jacketed transfer lines to maintain temps while you remove the plant matter from your solvent. As the temp rises and you have plant matter exposed to ethanol you will start pulling a ton of green and the tighter micron bag you use the longer the separation will take. Also the centrifuge will add heat. I would also pay to get both systems wrapped with high R value insulation to avoid Lake Tahoe on the floor below. A scrapper or auto discharge centrifuge and very large jacketed mixing tank can turn this setup into a semi continuous extractor. Feed your filtrate from the centrifuge into staged 12” pressure filters and an inline heat exchanger prior to evap and you are rocking!!!