With your clumsy hand, hold two linear filters crossed, to block the light.  Use your clever hand to insert the 45 degree polarizer in between.
<a href="//commons.wikimedia.org/wiki/User:Guy_vandegrift" title="User:Guy vandegrift">Guy vandegrift</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>