You may want to check out Photo stencil QFN/BGA Repair tool

I'm a little confused because your email says the components are leadless, yet at the same time you say they have 20 leads.

I am going to assume they are leadless components with 20 attachment sites.

Without seeing these devices, my suggestion would be to put solder paste on the pad sites, place the parts and reflow them in an oven.

Leadless devices can bridge without proper stencil design. There is a design formula used to determine proper deposition to wet the pad, create a good joint, and avoid bridging. Once rework becomes necessary, there are two ways to deposit paste. Print the board or print the component.

For printing the board, a small stencil could be made to clear neighboring devices that have already been loaded. This method has some challenges, such as registration issues and squeegee room.

The simplest method would be to use a component printing fixture and stencil to deposit paste on the component leads (similar to a BGA re-balling fixture). Then, place the component and reflow.