Thanks for the post.
A tea press works the same way as the "french press" associated with coffee (it usually is a french press, actually): the tea leaves are pushed to the bottom of the pot, separating them from the water. I don't recommend this, as it usually produces bitter tea.
Plastic infusers may not be the best -- you have to make sure that it is good quality plastic (like the ingenuitea, which is highest quality food grade plastic). When plastic is heated, it can add unwanted flavor, as well as some nasty chemicals. Stainless steel infusers are better, but still impart some weird metallic flavors. Glass infusers are good, but the holes are usually too big for some of the smaller teas (as you mentioned).
Probably the best infuser for you (since you already have the ingenuitea) is the Mikado Gold. Gold infusers impart no flavor, and the mesh is fine, allowing for a leaf-free infusion. Here is the link:
Hope this helps,