Hi, Sue!
Remember... I'm not an expert... I've just played around with stuff like this over the years. And it did seem to make a big difference in the apple crop when our wild bees were MIA.
First, while I did say "paintbrush" and you CAN use one- you really don't need one. It might be easier for some crops, but...
When I did apples, I picked a small branch off either a wild tree (lots of them around here) or a variety I knew was a good pollinator (if you aren't sure about what you've got, read some catalogs or look up on the 'net what varieties will pollinate what). I'd take a freshly opened blossom and pull the petals off, leaving the stamens (the male parts, which are heavy with pollen). Then I'd dust that blossom on the main ("king") blossom of each of several blossom clusters on the tree I was working on. I figured I could do a dozen or more before switching to a "fresh" flower for more pollen.. and it did work.
One really good thing about this is if you ARE the main -or only- pollinator working, you can pollinate only the blossoms within reach, and only one on each cluster- which will eliminate the hand thinning usually needed later on.
As far as "speed tricks" you might be surprised at how fast you can get this done if necessary, although I don't believe it will be practical to do an entire orchard. I used to get good crops from my 8 front yard trees by spending maybe 1/2 hour a day every day for a week or so. I'm not sure time of day matters much, but I preferred to work in mid-morning- about the time the sun warmed things up and when bees would normally be buzzing around and working. (Time of day can be critical if you are attempting plant BREEDING, where you need to beat any pollinators to the flowers, however)
For all the little details for whatever plant you're thinking of producing, get your hands on a good seed saving or plant breeding book- "Seed to Seed" is one, and "Breeding your own Vegetables" is another. They have a lot more detail on other aspects (the genetics of plant color, for example, in the latter named book) but they also give really good basic information on what plants will pollinate each other, and many of your other questions.
For pumpkins, squashes, etc, you can either pick a male blossom and do the same thing as I did with the apples, or you can use a paintbrush- a nice, fine bristled plus round one works well- and swish it around in a newly opened male blossom, then dab it in several fresh female blossoms, before "reloading" it with pollen from another male. If you're trying to save seed, wash the brush out thorougly with fresh water before going on to a new variety of plant which could be cross pollinated (zuchinni and yellow crookneck squashes, for example, or pumpkins and winter squash. Again, this is where a "seed saving" book is valuable)
As far as blueberries- at this point, I'm as clueless as you! I'm going to be doing some reading up... I'm assuming (always a dangerous practice!) that they are similar to apples- that is, each blossom has both male and female parts, but they require pollination from a different variety to produce fruit. (This is known as being self sterile, by the way). I'll probably experiment with picking several blossoms, picking the petals off and using the cluster of stamens to brush across many blossoms at one time... and then try a paintbrush and see if that is easier. The drawback with picking blossoms and using them as pollinators is- obviously- that the blossoms that you pick won't produce fruit themselves, where if you use a paintbrush and go back and forth between blossoms, each bloom can produce a berry. For large fruits- apples, pears, peaches, etc- that's not really a problem because they produce a lot more blossoms than they can possibly support as ripening fruit. For the smaller fruits, you probably don't want to steal many blossoms just to use as male pollinators, which is where the paintbrush may come in handy....
And yes, I'm praying for healthy bees as well! As I said, it has such huge implications for more than just our gardens this year... everything from the large farm crops to next year's seed crops will be affected if this CCD spreads. Scary times...
Summerthyme
