There is a fast technique of germinating fruit seeds with hard seedcoat like the seeds of chico, atis and guyabano.
With the use of a nail clipper, clip a small portion of the tip of the seed. This will allow moisture to get inside the seed which will hasten its germination. Without nipping the chico seed, it will probably take six months before it will germinate. By clipping, germination could take just a couple of weeks or thereabouts. The same is true with seeds of atis and guyabano.
You can use a mixture of garden soil and compost for germinating. You can germinate the seeds in a plant box of seedling tray. When they will have four leaves, you can transfer them into individual black nursery bags with 4-inch diameter where they will grow into ready-to-plant seedlings. These can be used as rootstock for grafting. That’s in the case of chico.
For atis and guyabano, the seedlings can planted in the field without grafting, unless you want to graft a special variety.