Change to a different process. MIG welding ALWAYS, always,
always creates spatter.
How you stop excessive spatter is by adjusting the voltage and
wire speed. Lower voltage and faster wire speed = more spatter.
Higher voltage and lower wire speed = less spatter. How you find
the magic combination for the weld you are making is to test in an
inconspicuous place - run a bead, check for spatter, adjust the two
settings, run another bead...eventually you will get to the point
where you're getting a nice weld with an acceptable amount of
spatter, and then you weld your project with it.