BILL J. - I tried Slip-Plate for a couple years with so-so results. I just don't mow wet grass anymore.
RODNEY K - Welcome to the forum. I have a lot of trees on my 2-1/2 acres, so deal with leaves every fall too. Several of us here have lawn vac's we pull in the fall when we mow. I built my own patterned after a brand called TRAC-VAC. They're expensive, the model I sorta copied was $2000 list and I spent about $400-$500 for steel & materials to build mine. I incorporated a few improvements to the design on mine so I could trim around all my trees better too.
Another vac to look at is made by AgriFab, they're cheaper but a decent unit. There were vac's made for Cub Cadets years ago by the name of Peco, and of couse the newer brands like Cyclone Rake.
I pulled a 30-32 inch Parker lawn sweeper for many years but it was a lot of work, emptying the sweeper into a cart then emptying the cart. My vac uses the same cart I use for normal yard chores but I made a top & sides for it, so I make a brick of leaves/clippings 32 inchs wide X 45 inchs long X 36 inchs tall. Since I load on the go they pack in and settle pretty good, I guess-timate I get 600-700# of leaves/clippings per load, maybe a bit more. Loading the cart is the easy part now, but I've been tempted to put a "Live unloading floor" with a conveyor belt or chain in my cart so I can unload without having to dig the stuff out with a pitch fork or rake. I normally get between 20 and 25 loads of leaves/clippings every fall. I used the vac about 3 weeks ago to pick up dry grass clippings, got eight loads in about 3-4 hours, about 8000# of them!