I have a question about faking MAC address.

Since i have only 1 computer, i cant test MAC filter bypass on my router.

So.. here goes.

A client is connected to a router.

When i fake my MAC address to client's address, can i do a fake auth with that address without kicking off a connected client?

If i must kick off a client, how do i do it? Do i do a deauth attack, then immediately a fake auth..?