I've played the level like 36278478 times, and I just can't get holy cow... Any advice? I keep having dairy cows walk into me or hitting signs.

All I can tell you is to -- well, keep practicing. And, of course, to avoid the cow-heavy spots.
It's been a while since I've beaten the level (and ever since, I have this aversion to collecting cows in the main game) but I do recall staying on the upper level for as long as I could. Once you're big enough to grab 'em, get the sunflowers; they help add to your diameter. (Avoid the Cow-on-a-balloon, of course.) Near that spot is a little alleyway filled with people; they help too.
Oh, just so you know, there are two Holy Cows on the level -- one is in the park, and the other is wandering in the forest way up by the farm.

Go for the one in the forest. It's easy to get there and he sometimes goes over to the edge.

yeah, basically patience is the key

The Holy Cow was the next to last item I got. The minimum size to pick it up is in Vix's faq (7m 8cm 8mm). That's the size at which when you hit the Holy Cow, it flies upside down and then you can pick it up. I learned that the hard way because my Katamari was just over that size when I dove from the upper parking lot straight down into the park. The Holy Cow flew upside down, off to the side and the Katamari touched a Cow Man. :eek

The Holy Cow by Seaslug Farm is easy to spot when it's not in the trees. Otherwise, you'll grab one of the several little cows wandering in there also. But the Holy Cow does come out of the trees every so often. If it does and you are the minimal size, be sure to try to knock it away from the trees, otherwise you won't be able to see it to pick it up and you'll accidentally grab a little cow.
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I've also played this level about 6 million times. Am starting to detest cows. Any detailed advice on getting big enough in the upper level appreciated.

I know everyone else has moved on to We Love Katamari and Me&My ... don't laugh. I'm purposely trying to work through as much of this game as I can before I move on to the others, now that I know they're probably all we'll ever get. I like it so much that I want to stretch it out, if that makes any sense.

But I'm getting so frustrated over Taurus that I might just say the hell with it and get the next game!! Taurus is starting to feel like a job. Only one time have I gotten big enough to get the Holy Cow, and I did get to the forest to wait for him, but I ran out of time. ARGH. Generally I get to around 5m and a little and either get down to the park, but not big enough, or hit something by accident.

Thanks in advance y'all!

Oh, I think Taurus is worth sticking around for; it felt mighty rewarding getting that Holy Cow the first time. If you ask me Holy Cow is harder to get than the Cowbear in WLK.

I stay in the upper town until I reach 3 or 4 meters, then carefully avoid a couple floating calves and drop down to the "Paradise" area. I pick up most everything in the lake, then head for the beach, then believe it or not I enter the walled Seagull Park. To do this I (make sure Cow-man and Calves are far away then) climb onto the base of the wall then go left to where I'm just above the beach, and force my way up and over the wall. Seagull Park is good for a size boost. Then I go back over the wall, go clockwise around the outside of Seagull Park to the area with oxen and palm trees, and I climb up into the upper town and reach 6m44cm so I can get palm trees. I do that, then head back up into the upper town on the way to the highest hill, keep circling the forest until I see Holy Cow near the edge, try to hit him so he won't end up in the forest, and mmmmmmmmmmmmmmmmmmmmmmmm, beef.

(Sorry Holy Cow, I don't actually eat her, just roll her up to be honest.)

When you are big enough, you can get to the park from the sea (good way to avoid accident with smaller cows, too) go clockwise around the wall until the cliffs block you, then face the wall and climb. Beware, though, 4 cowmen surround the holy cow so you have to aim between them..

Thanks, you guys! I had avoided going into the actual park but will add that to my routine!

I usually stay only in the upper town. There is enough if you get all the trucks, and then at around 6m44cm you can get palm trees on the beach, and then you'll be almost big enough.

One HUGE problem I've had is that when I hit the holy cow, he flies into the air, and through the ground. He literally falls through the level, meaning it's impossible to get him and the play through was useless. I can do the level in about 4:05, but the one thing I absolutely can't avoid is that sometimes the game just freaks out, and that happens.

Anyways, tips, cars are really important, especially lite trucks, the two by the slope down to the beach, the one on the far end of the beach, and the one by the cows on the concrete platform on the way to the ranch. Also the big boulders, the one on the hill to the ranch, and the two on the hill down to the beach.

I hope that's helpful, or if you already have it, then congrats.