my friend, yuo have bristle marks, that or you have a brush that isnt meant for use with solvents (i.e. nylon or some other synthetic bristle), what can happen if you use a synthetic brush with an oil based coating can make the bristles of the bruch fall out, fray or stick in the solution, if that's not the case then the bristles may be too stiff and making little furows in the urethane as it settles. the solution? foam applicator

as far as your streaky appearance, that could be several things. firstly, all finishes that come in a satin are manufactured as a gloss, flattening agents are then added to the mix to make it that duller sheen. the solution? stir thouroughly. Stirred not shaken, opposite of james bond's preference. shaking can put bubbles in it

as with anything with a pigment, sreaking can occur if the solid pigments in your coating float or settle, making some spots darker/lighter than other spots. the solution?? you guessed it, stir.

the flattening agents settling coupled with the pigment settling can give you some odd effects as far as how it looks when it actually goes on, a good solid stir can fix alot of your problems, also, that foam applicator will make for a smooth finish. poly hsades isnt a bad product, nearly all of the molding in my house is coated with it, it just takes a little background info to make it look right

Water based stains tend to raise the grain. One way to deal with this is to wet the surface, let it dry, and then sand off the "fuzz". I tend to use an oil based stains when I can just for expediency.

It doesn't much matter how you apply the stain because you're essentially flooding the surface and then wiping off the excess. Use a brush, rag, whatever to spread it out relatively evenly. Allow it to sit until the desired color is achieved and wipe off the excess.

For a top coat, I prefer a wipe on finish. Because they're thinner they take longer to build and you'll need more coats but I find them more forgiving in terms of application.

never use the polyshades, as it is very hard to get a good finish. You should use a gel or traditional stain, then a polyurethane.

never use ployshades!? what!? i will repeat this- nearly all of my house is covered with this stuff one way or another. it looks great and i am by no menas a professional, ill take pictures if you dont believe me, want something thats not user freindly? try using a water based stain and top coat it with high build polyurethane i can assure you that its nearly impossible and anyone thats ever done it will tell you the same

I am a professional finisher and can tell you lots of horror stories about people who have tried Polyshades. I won't repeat my opinion of it here (again).

I'm glad it worked for you and you like it.