Yeast cells and blood cells are roughly the same size, so any hemocytometer will work. Don't worry about the different grids between different models, just make sure you follow the directions for the one you have. The ones I have used have 9 squares, but you only count from the corners. The corners are further subdivided into 16 squares, and you don't need to count every square to get a good estimate of the cell count. When it comes to ones on the line, come up with a way that works for you and stick to it. Typically, I count cells partially in the square on 2 sides, and not on the other two sides of the square.
Your biggest problem is going to be distinguishing live from dead (Are you going to be staining?) and breaking up the clumps so you have individual cells to count. I don't think you'll want to spring for a vortexer, but if you pipet up and down that can help break things up. I've heard of people using "marital aids", aka personal massagers, on the bottom of a microfuge tube to break things up too.
Also, make sure you take accurate measurements for your dilutions, and make sure each sample is uniform before you dilute it again.
Which brings up another point, dilute your sample! You don't need to count every cell from a thick slurry, dilute it 10-fold, look at it under the scope and see if it is too thick, if so dilute it again, repeat until it is reasonable to count.
Oh, and get yourself a clicker counter thing like they use to count people going into places, it makes the counting a lot easier and faster.
I hope that helps