Tyler will relate to opting for the shed made foam donut option.
Definitely can MF - I can make one in 2 minutes that will last longer (the victa ones seem to squash flat and turn to powder in no time). $1.60 each is nuts for a small piece of foam5 considering I am currently using off cuts from clark rubber that cost $5 and each can make 15 or more
WD40 is pretty useless - penetrene, 1:1 acetone ATF or (at a pinch) 5.56 CRC will all run rings around it.
That being said, it is a good water dispersant. Got 10l worth of WD40 equiv at repco clearance for $15 and refill one of these.
https://www.bunnings.com.au/wd-40-330ml-non-aerosol-trigger-spray_p0108296Spray beneath the mower decks to help with build up so its quicker to clean after each mow