Rita, as you said, the little bulbs are easy, big bulbs like Daffodils take some work. Choosing varieties that are specified as good naturalizers or perennializers is important. Those are vigorous enough to emerge through thick sod and multiply well. One thing that makes it easier is to order "landscape rounds", smaller bulbs that are easier to plant, usually single nosed bulbs that will each produce 1 bloom. Also, some of the best naturalizers are small varieties, like Jet Fire or Tete a tete, that just naturally have smaller bulbs. A trowel or bulb planter can be used for smaller bulbs, I used a trowel to plant the 'February Gold' in the pic. The grass was already thin there from the pine needles, so cutting through the sod wasn't bad.
For some of the big bulbs that I've planted in lawn space, where the sod was thick, I cut out areas of sod with the spade, peeled them up, and laid them aside. Then cultivated the soil, and planted the bulbs, and put the sod right back in place. For say 20-50 bulbs, I cut out a larger section or two, then some smaller clumps around them, tapering to small clumps of 3 bulbs. That was my effort to have the appearance of large clumps that have increased naturally, and it worked well.
Earlier flowering varieties are best, the foliage gets finished doing its thing faster for mowing. I'm not sure about some of the little Irises, but the Iris reticulata cultivars grow taller foliage after the flowers fade, so I don't think it would be a good one for lawn use. I have no experience with I.histeroides(sp?), not sure if the foliage does the same thing.
