You do not say what tank you are using.. The JOBO Expert 3010 will hold up to 10 sheets of 4x5 and can be used by rolling it manually across a level surface. The advantage of the JOBO tanks is that they will allow small one-shot quantities of chemical which can be used and thrown away without loss relative to the capacity of the developer. The Expert 3010 has a minimum fluid requirement of 210ml for complete coverage of the film. Practically, this means that you use the quantity of developer required for the film area, not some larger amount to fill the tank.

For small numbers of sheets look for what is called a "slosher". Googling "film slosher" will bring it up. This, however, requires more chemical and a darkroom.