OMG! Bwaa, haa, haa, haa!!!!!! That picture is just WAY too hysterical, thank you Allison Finch I really needed a good hard belly laugh!
Okay, back on topic...
I also find that starting with a clean as possible horse helps as well, does not dull your blades as quickly.
Oh, and if you can clip about 2 weeks before you are going to show, that gives time for the hair to "blend".
I use a wahl adjustable clippers. Its really reasonably priced but works great and saves you money on extra blades in different sizes. Biggest thing I can recommend is make sure he's clean and make sure you have the right size blade on. Theres nothing worse than using a short blade on legs accidently. Whoops!!