The Micro 20 or 3/4" block maker is an amazing tool. It blocks 20 spaces for seeds with 3 times the amount of soil of a 1" tapered plug. It is a space saver. You hardly need any space to whip up 20 seedling cubes. But, this machine does have certain particularities that you might not be aware of at first glance. First, the best potting soil to use is simply peat moss screened over a 1/4" hardware cloth or screen. With 4 parts peat, 1 part vegetable compost (or worm castings) and a handful of horticulture grade lime and rock dust you can create hundreds of successful blocks for little or no money. The mix should come out stiff but not dry, thoroughly wetted and moist, but not soupy. Second, such a small machine will have two types of users: one with big hands, and one with small hands. For the small handed folks, using two hands to charge the blocker seems appropriate. Pack your blocker in a shallow plastic tub. Use your pointer fingers and thumbs, and push into the tub over and over and pack it tightly. For the large handed users like myself, use one hand and hold the ejection mold and pack and turn and pack and turn. Using a flat wooden surface works fine, just pile the soil in a heap over and over again. Scrape it against a real flat blade, like a trowel or a dull knife or thin piece of wood. But, a bit of advice from the Guru: You simply may opt out of the scraping the blocker step, as I have found it leaves a less desirable block. Try both ways, first. If you don't scrape, you'll want to press the maker firmly on the tray to flatten out the bottoms. Your blocks should come springing out and be perfect little squares with a nice seed hole definetely indented. Anything less than perfect is not acceptable with the 3/4" blocks. You should be able to pick them up easily; firm, strong, solid, crisp. It will take a few times to find the sweet spot. Third, lay them on a small square of plasic or a recylced plastic container of some sort. I'm not a big fan of wood anymore as it seems to dry out too fast. Wood works fine if you're constantly watering. But, even better is some recylced plastic container with a shallow lip around it to hold in some water for easy watering. DO NOT LET YOUR MICROS DRY OUT! You could lose valuable seeds, quickly. Now let's talk about what to grow in Micros.
In my experience, tiny seeds for flowers work best in Micros. We are planting more and more flower starts each year, and the space saving benefits are miraculous. Seeds that take a long time to germinate are perfect because you don't tie up all that space waiting for seeds to germ. Classic examples would be flowering tobacco and alpine strawberries. They can sit there a month before anything happens. As far a vegetable seeds go, parsley and celery are best started in Micros. If you are a market gardener or nursery owner, tomatoes, peppers, and eggplants are the norm. Not that a home gardener shouldn't use the Micro, if that's all you've got, but I would just use the 2" blocker if I had a small amount of seedlings of those three to start. Then you have to change out pins for transplanting, and that's a little time consuming for home gardeners. I have a dedicated 2" blocker for every pin, so I don't change them out anymore. Make sure to cover tomatoes, peppers, and eggplants with black plastic to keep the moisture in after watering, and it help heat up the surface. Transplant quickly for these three, because their roots are already three times the size of the seed leaves that are visible. Note: If you have let them get too lanky and tall, just transplant them on their sides convering up the long stem with soil. They'll just grow roots on the stem and your plant will be stout and strong. The best transplanting method is using a grow tweezers. You might have to make your own. Just take two wooden plant label stakes about 6-8" and staple or tack them over a 1" dowel at the end. You could also use some scrap metal for a spring taped around the stakes. You could use some cedar shims split to 3/4" and some metal wire spring or sheet metal or the 1" dowel for the fulcrum end. If you find one, a tortilla flipper is PERFECT. Always dip your tweezers in water before plucking out a block. The ends should be fairly thin and sharp to push in and cut or separate the blocks from each other. Transplant immediately to your prepared 2" blocks with 3/4" cubic pin. Push down firmly to release all the air gaps. Water with a little willow branch water for root growth, or kelp fertilizer to ease them in their new home. With a little practice the Micro 20 will become the most amazing space saving seed starting invention you've ever used.