Pollination has always got a degree of hit and miss about it. honey bees have certainly become the most effective pollinators, refining a rather random system.
In general a pollinator will land on a flower (normally to collect the sweet nectar inside). In order to achieve this, the pollinator will have to move past the stamens of the plant (where the pollen is produced). When the pollinator moves on to another plant, it brushes past the stigma of the plant, brushing off the pollen from the previous plant. If the two plants are the same then the pollen becomes fertilised and a new plant is born.
Of course most pollinators move randomly between flowers, meaning that much pollen is wasted.
Honey bees are different. An individual honey bee remains faithful to one sort of plant for it’s whole life. This means when the honey bee moves between flowers, the pollen it is carrying is perfect for the next flower.
This means honey bees produce more flowers and more nectar for other pollinators.
Solitary Bees will fly a much smaller area, however are much less efficient at collecting pollen. This is actually better news for flowers as they drop more on the flowers, pollinating more flowers.