The obvious place to go for the answer to this question is the United States. The US has just drawn up a plutonium disposition policy to dispose of 50,000 kilograms of surplus plutonium from old nuclear weapons. The exact amount to be used in MOX or to be immobilised has not yet been decided. Many methods were looked at, studied, and discussed in great depth. There remain many problems to be overcome with the least publicly popular option in the US of using MOX in civil nuclear reactors and the future of the US MOX programme is by no means certain.
Vitrification is, however, a well-established technology.
This nuclear waste is mixed with borosilicate glass and turned into glass logs. BNFL are world leaders in this type of technology and have a plant currently in operation at Sellafield. However, the conversion process used to produce the PU oxide would be the same regardless of the immobilization technology used. This step involves removing the surplus Pu from storage, converting it to a suitable oxide form, packaging it, and transferring it to either the glass or ceramic immobilization facility. Also, all steps after the small cans are prepared are the same for both glass and ceramic immobilization.