My first strongman comp is fast approaching and grip strength is a weak point.
The deadlift event allows straps, so although speed will be sacrificed with straps i think using them at the heavier weights will save my grip for the later events.
The max distance farmers walk is obviously going to come down to when grip gives out, my grip will fail well before any other part of the chain.
How would you go about rapidly increasing grip strength for a max distance farmers walk in 4 weeks?
What’s the course like? 1 long straight shot, or a short distance where you’ll turn around and go back and forth, then turn and back and forth? If you’ll need to turn in the competition, Be Sure To Practice Turning.
For training, probably a linear plan, like 70 or 80% of comp weight for 2-3 runs the first workout. Then a little heavier and a little heavier, dropping down to 2 then 1 run, until you take a little break right before the competition.
Odd Haugen has lots of content about grip strength. Not sure how fast it will help, but he is a beast.
25m length, so turn…hopefully turns 
Ive been doing 2 or 3 max distance runs with around 75% so not far off what you mention.
Then on deadlift day ive been backing weight off after last set of deadlift to a weight that challanges my grip and just holding on for as long as possible.