Reddit mentions of AFA Tooling Deburring Tool with a Blade and Pack of 10 Extra Blades

Outside of the things others have mentioned (springs, tubing, couplers, SKR, BMG, etc.) - if you don't already have some good tools/spare parts you can use this time to invest in some.

• Some superlube for bearings/z-rod/etc
  
• Ferrules & crimp (great if you want to swap boards and have 'proper' cabling)
  
• A heavier duty 'get off the damn bed' thingy
  
• Reusable cable ties (save the ocean or some shit)
  
• Deburr tool
  
• M2/M3/M4 bolt set with T-nuts (great if you want to print some add-ons that attach to the extrusions)
  
• Different bed surfaces if you want to experiment
  
• Microfiber cloths for cleaning things
  
• Tooth brush and some orange cleaner for cleaning up that z-rod
  
• LED lightbar or some other form of lighting
  
• Extra hot end socks, nozzles, thermistors, heating elements (better to have one or two on hand then wait a while!)
  
• 14/12 awg silicone wire for mains connection (great with spades & ferrules!)
  
• Soldering iron, cabling, heatshrink (if you want to swap fans or do any other wire splicing activities)
  
• Ball bearing 4010 fans (or 4020, or whatever size you mod to - IMO go for 24v and avoid noctua/buck converter shenanigans)

A fairly simple method:

• bend the brim first against the model and then backwards - repeat a couple times and the brim will fall off
  
• use a deburring tool (sample only - first link I found) to remove the remaining brim.

I use a deburring tool to remove brims. Works great.

something like this

Try using a deburring tool to chamfer the edges of the cut.

Something like one of these?