I only use compost at or near the surface. I rarely dig it to a depth greater than a few centimetres. This is usually done by tickling it into the surface with a rake or weeding fork. Compost placed on or near the surface will be incorporated by worms and other soil animals.
If the soil is exposed to sun or wind, cover the compost layer with mulch to protect it from drying out.
Few of us are lucky enough to have all the compost we would like. About 2- 4 centimetres of compost addition per year would be ideal for most vegetable gardens. If you have much less and want to spread it around the garden, make a mixture in the watering can and water it on - this will improve the effectiveness of a small amount and is better than dry broadcasting a thin layer.