how long do i cook potatoes in the oven for? they are small-med russett potatoes. i poked holes with a fork?!

That's the right temperature. Leave them in there about 45mins to 1 hr. You can use a pot holder to squeeze one to see if it's soft to tell if it is done.

An hour and a half, at that point take a fork and put it into the potato, if it goes in smoothly without any resistance, it's cooked.

Try this, slice the potatoes into 1/2 in. slices, in a baking dish fan them out like a deck of cards, salt and pepper, lay some pieces of bacon on the potatoes, cook for 1 1/4 hours.
Put foil on the top of the pan, use red or yukon gold potatoes.
I like to slice up some onions and red bell peppers and put them on the potatoes before the bacon.

I think you have the right temp. The time should be 45-55 minutes. I have this set of baking nails, and I insert them into the potato after I wrap with the foil (lengthwise). When the nail pops out of the potato slightly then it is done. Also squeezing in the middle of the potato helps to check for doneness. Usually when I bake potatoes, I will bake 8-10 at a time. Then I will have them to serve in other ways throughout the week, and no hot oven.

Mama say

You shouldn't put them in foil, the skin (which is the best part in my opinion) will not get nice and crispy! But anyways, you should cook them at 425 for 45 minutes to an hour. Till you can pierce them with a fork and they are tender.

about 50-60 min

5min per a potato