If your reusable nappy does not have a stay dry layer, you can, if you choose to, use liners to catch any solids and flush them down the toilet.
Disposable liners help you on your real nappy journey and can make the job of using reusable nappies a lot easier. You do not have to use paper liners, it's a personal choice. Fleece liners will work just as well and are reusable. When potty training, we recommend removing any fleece liners from the nappy a few weeks in advance. Fleece liners provide a stay dry layer, and it helps if you remove this for potty training, so your child can begin to feel the wet, and connect the cause and effect dots! Not all disposable liners can be flushed, check with the manufacturer! You can use any brand liners with any brand nappy, eg if you have bambino mio nappies, you don't need to use bambino mio liners, you can use little lamb liners.