The all in feature works best when you combine it with strong coatings since that minus 5 to hit can be rough starting out. Grab some oils of accuracy or sharpness, they'll help offset the penalty and let you land those big hits more reliably. The really interesting part is using crawler mucus, since paralyzed enemies are basically free critical hits which triggers your bonus attack

For maximum effect apply coatings before combat starts so you dont waste bonus actions during the fight. Remember your bonus attacks from kills or crits are way more valuable than reapplying coatings mid-battle. Purple worm toxin adds nice poison damage that stacks with your plus 10, but save it for when you've got advantage or fighting lower AC targets

Just keep in mind you need heavy weapons like greatswords or halberds to make this work, and those accuracy penalties can really hurt against tough enemies. Maybe interesting - if you time your coating applications between fights, you can keep the damage flowing without sacrificing your bonus attack chances when you score kills