My home river, I live 12 minutes drive from it.
The Grand is wide, shallow and in the lower reaches it often runs quite dirty. It has many stretches that are ideal for swinging a fly and is one of the few rivers in this neck of the woods where there's room to swing a 15 footer.
There is no stocking on the Grand so the fishing is quality, not quantity. One fish a day is considered good. It's a big river and being shallow, there's lots of room for fish to spread out. Like any river, local knowledge can improve your odds.
Brantford and above the river runs fairly clear while from Caledonia on down, the river can run dirty with visibility often less than one foot. Nevertheless, good fishing can be had in these stretches when large, dark patterns are used. The lower stretches can clear up when we've gone a week or so without rain. The closer we get to December, the clearer these stretches will run.
Unless the flow rates are up (above 50 cms in Brantford/York) most of the river can be fished with a floater, a long, skinny leader and a fly that will get down. High drag and/or slow sink flies will need a sinktip. A 15' Type 3 will fish well in most places as will an extra fast 10' poly. Whatever you use for flies in NY will work here so no special patterns are needed. (My friends and I fish both sides and we use the same patterns).
Flow rates can be found at the Grand River Conservation Authority:
http://www.grandriver.ca/index/document.cfm?Sec=2&Sub1=6&Sub2=4 This site also has a river map where you can locate the towns I've mentioned. Rates above 80 cms in Brantford and York will be tough fishing. 35-50 are ideal.
Any Spey casting rig wil work here, so whether you're a Skagit fan, love your Scandi heads or yearn to chuck a long belly, there's room for them all.
Rods can be anything you like. I tend to use a 13' - 8 wt. or 14' - 9 wt. for most fishing, but some guys are out there with 15' -10/11s as I have at times as well. Switch rods and single handers will work fine if you parse the river well and pick your spots. It's about 200 yards wide in Caledonia and we can wade across the entire thing at 50 cms so there's lots of flexibility for any rod size.
The season from Paris on down runs from the last weekend in April to December 31st. Some stretches require a barbless single hook, no bait, C&R only so if you're planning on keeping fish, know the regs for the area. All the legal info can be had at the Ministry of Natural Resources:
http://www.mnr.gov.on.ca/en/Busines...&CSB_ic-info=fishing-in-Ontario_text-link-Eng
If you plan on C&Ring or maybe only keeping a fish or two, then buy a conservation licence. Much cheaper. Regular licences assume you plan on filling the freezer and charge accordingly.
Send me a PM when you're thinking of coming up.
