Hi Bonnie, sorry I haven't been on in a few days and just got your message today. I'm not much help when with the "pet" clippers as I've only used professional Andis clippers. I did buy a "pet" set when I first got Morgan before I learned to groom and I hated it. The clipper was loud, got hot quickly, and I managed to break the plastic combs. I don't remember what brand it was though.
I mainly use my Andis 5 speed, but I also have similar clippers to Jenny that are a little cheaper and better for your use.
Andis UltraEdge 2-Speed Dog Clipper | PetEdge.com and
Andis AGC 2-Speed Clipper w/ #10 Blade | PetEdge.com. The first one I bought after I broke the plastic combs on the first crappy clippers I bought from Walgreens. I also purchased a few blades to go with it. I still use these clippers as backup. The second set was given to me when I went to grooming school. They are similar to the Ultra Edge except a tad slower. There is also a single speed clipper that would be good for home use as well since you're just grooming yorkies.
Andis AGC Single-Speed Clipper w/ #10 Blade | PetEdge.com
I also have these
Wahl Arco SE Limited Edition Pink Cordless Clipper Kit | PetEdge.com which i just used to cut morgan down two weeks ago. Since she has a thick cotton coat I used the 9 blade setting on her body and then use a comb attachment and scissors on her legs and head. I like her really short in the summer because she gets hot and I'm too lazy to comb her legs after they get wet in the morning when the sprinklers go off right before she goes outside to potty.
(these are similar and very nice
Wahl Color Bravura Cord/Cordless Clipper | PetEdge.com I used them to shave a few cats in school.)
If you get a clipper that uses detachable blades you can use any blade brand you want and don't have to stick with the same company. I prefer Geib Buttercut blades and Andis Blades. You can also use Whals and Osters. I'm not sure how well the master grooming and petedge ones work.
Here I used a 7F all over on Morgan and scissored her head.
In this one I used a 7F on the black parts of her body and a comb attachment/scissors on her legs and head.
And in this one I used a 4F on her black body to keep it slightly longer and just neatened up her legs with scissors and thinners.
Morgan usually starts off in the spring with the first cut, then I just cut her body down and leave her legs alone the rest of the year or just scissor them up to neaten them. Sometimes instead of a 7F, I will use a 4F or 5F in reverse (going in the opposite direction of her hair growth) to make her hair even shorter. I also like to go in reverse on silky coated yorkies because it makes the cut neater and even all over. You have to be careful with silky coats because sometimes they have really sparse coat and if you go too short it can look like you balded them. Always start with a longer blade first if your not sure. This way if you want it shorter you can change blades. Just remember, you can always cut off more if the length isn't short even but you can't put it back on if you cut it shorter then you want.
As far as clipper spray and oil goes, I never use spray coolants. They cause residue build up and can ruin blades if the blades aren't cleaned properly after use. I have multiple blades of each size so if a blade is getting hot I can change it and use a cooler one. The hot blades I put on a cool counter top that is made of glass, metal, ceramic, or tile because it will draw the heat out of the blade faster to cool it. I use oil before, during, and after each blade use. If your blades are clean and oiled they will las longer. If they are not oiled properly they will heat up faster and wear down faster. I put a dab of oil on the tracks of the blade and slide the cutter back and forth to distribute the oil. then wipe off the excess with a towel before putting the blade on a clean coat. here is a video:
http://www.northerntails.com/images/BC-Titles.wmv this site also has many other clipper care videos
Videos for pet groomers