Ospho.... a bit more gentle than muratic acid and works just as well. You can use it on the ITS as well, just don't leave it on there. Spray on, wipe and spray off.

Bottom
 

The best way is to Yard Arm the boat off it's trailer, acid treat the bottom and polish and wax the bottom.

Steve, How long will that prevent in the Grand River? Month? Summer?

I use Sea Safe hull cleaner works great and doesn't hurt the trailer like On&Off and other acids etc....a good waxing helps tremendously but I never been able to prevent scum for more than a few weeks. But it makes it wipe right off if you hit it immediately while its still wet after you pull it out. On a smaller boat you can get away with jumping in the water and rubbing it off. Obviously not gonna happen on a big boat.
Also depends on the water quality. 1 day in the CT River and my boat is already yellow LOL. 2 days in my lake usually doenst leave any scum tho.

slimy grimy always seemed a lot less hard on the gel to me.....

Every time I take it out I spray scum line with Starbrite Black Streak Remover and wipe down with a towel(while it's still wet from being in the water).
For the yellow stain;
Step 1-Starbrite Black Streak Remover, car wash brush and water(sides)
Step 2-Starbrite Hull Cleaner, car wash brush and water(sides)
Step 3-Boat Wash Gel, car wash brush and water(deck)
This has never done anything to my aluminum Myco but I keep it plenty wet during the cleaning.
I use this for the drive area
https://www.ebay.com/i/362197529855?...8f675a5226a6b8
Works good on rims too

Should last the summer,

Anyone find something that won't mess up bottom paint? I've used On Off and Slimmy Grimmy and both left white streaks on my bottom paint.

Let me know if you want your bottom done, i have a few openings coming up , you should still have my cell number.

On Off then wash &wax