setting 1'x1'' tiles on shower floor

If you set the sheets in grout you should be able to sweep them all up with a broom when the grout dries. Sounds like your main concern is thinset squishing up between the joints. There are few ways to mitigate that situation. Use a small v-notched trowel, 1/4." Using light or dark grout? Match the thinset more closely to your final grout color. For a small area like a shower pan, pre-fit all your sheets, including cuts. Don't overdo the mud, mix it and let it slake, you don't want it too soupy or too dry. Spread a thin even layer of thinset with no extra gobs. Tap it into place evenly so there is good coverage, you might try a piece of drywall and a rubber mallet depending on the pitch in your pan, to ensure that the tile lays flat. Wipe up extra with a sponge, if you put it down like a pro would there won't be all that much mud. Good luck

Small, thin mosaics can be a pain to work with if you're not careful. Depending on their thickness, I recommend using a square notched ⅛" or there abouts trowel. We usually don't use V when using thinset. V's are better with mastic on walls. If you're neat you won't have much trouble. If you get a little ooze, remove the thinset with a small piece of the box cardboard followed with a sponge wipe.

Beat the tiles with your grout float to set them, then wipe again as necessary.

As an alternative you could use an epoxy setting mortar that is also rated as grout. However, your choice of color may be limited to gray. This method works great, but it's more difficult and costs several times more.

A word about terminology. Some people on this and other forums keep referring to thinset as "mud". Not to be picky, but that is confusing and not correct. I think they do this because thinset reminds them of drywall mud perhaps. In the real world some call it "mud" to intentionally confuse people into thinking they're installing using the "mud" method. The "mud" method is a mix of Portland cement and sand placed on the floor about an inch thick or thicker to which tiles are later set on. Whole different thing.

Jaz