Medium Coverage - It has more coverage than the sheer but not as much as the full. This is for anyone who wants some coverage but nothing heavy. I would suggest you use concealer to cover spots if you have any, instead of using full coverage. MakeUpForever HD and Giorgio Armani Luminous Silk are my two favorites right now. Brush would be the ideal tool as sponge soaks up too much product.
Sheer Coverage - This would be for someone who doesn't need much concealing, but still wants to even out the skintone. Your skin will still look like skin. My favorites would have to be Chanel VitaLumiere and Nars SheerGlow. Brush or fingers to spread evenly.
Powder Based - This would be best for oily skin as it contains no moisture in it. They are usually very matte unless it is a mineral powder (which tend to have shine). Powder vs. liquid is usually a preference. Usually, powder is easier for people to use everyday and on the go. My two favorites are Laura Mercier and Stila. In addition, I love Youngblood (as I have previously posted), for mineral powder. Powder sponge or a tight brush to carry the product and help it set on your face.
Tinter Moisturizer - This is basically a moisturizer with a tint of color. This has no coverage what so ever. This would either be for everyday wear just to neutralize the skin a bit, or someone who has thick skin who shows no flaws. Fingers should definitely be your ideal tool for this, as you put on moisturizer with your fingers as well.
I occasionally will go back and forth with different products and brands. I used mineral foundation for the about 6 years; but recently changed into liquid only because I got tired of using the same product (still a HUGE fan of Youngblood). I may use a sheer foundation on a daily basis and change it up to a full coverage for events. You can definitely play around with it. One rule of thumb: if you are oily, stay away from luminescent foundations and if you are dry, stick with the moisturizing foundations. Always put on a moisturizer first to help the foundation slip better; but make sure you wait a few minutes for the moisture to set in your skin. Put the foundation on with downward strokes to help minimize the look of pores. Hope this helps...please let me know if you guys have any additional questions! Thanks.