Sitting wallows can be a very effective way to hunt bulls, most the time, like mentioned you have to put in the time. If I get near the wallow area and bugle and recieve a response, I'll bring the bull over to me, trying to stalk a bull in his bed, especiallyif he's got cows, is a no no in my book. If you spook him out of there by your scent or positive identification then that bull or bulls most likely won't be there to hunt them another day, plus that's a very low percentage way to get your bull into good bowrange. Here's another way to speed up the process, put the odds in your favor and most likely not spook him out of the area if a good shot at him doesn't work out.
If I know the wallows are there, as you do, and I felt a bull was bedded or within hearing distance on his way to his bed, I would pick out the most concealed wallow. (timber or edge of timber) Then I would do what a sneaky bull would do. First of all he wouldn't bugle his way to the wallow. (not looking for a fight) Hed get in there and splash around, be quite noisy with the splashing as you imitate a bull splashing, many times that itself will trigger a bugle from the real bull, if so stop and give a very short squeal ending with a low rounded growl and 3 or 4 submissive type grunts, splash loudly again like you're getting out and leaving, nock an arrow and be ready for his approach, don't call anymore. Make sure winds in your face and don't get out of bowrange of the wallow, the real bull will come to smell it over as all bulls will leave a scent.
If nothing responds during your splashing continue on with senario along with the calling, splash when getting out rake a tree or brush and stomp around some, give the same calling technique when done, and no more calling. Do all this in about a minute, just because a bull didn't bugle doesn't mean he's not on his way to check you out cautiously. If a bull is in the area you can bet he'll come on over in no more than 30 min or so, so don't move around and give yourself away, in a treestand or not.
As a side note, always pick the most concealed wallow so he has to come close to check things out. It doesn't matter if it's being used or not. Most the time when you find a wallow there's others around whether you've seen them or not, all it takes is one of them being used, but by you putting up a commotion in A wallow, this will still get his attention and direct him over to you.
There's a lot more on the subject, but enough for now!!!!!!!

elknut1