The simple answer would be that you are brushing on too much...so use less. But that makes the assumption you dont lnow any better...so I look for other answers. If it is an oil based poly it may be too thinned out or very old and lost its dryers...If it is a waterborne poly much the same but those often are thinner. So it the poly is new and not thinned, and the surface is sanded to 180 (not higher...it can close the pores)...you should be able to brush on enough to brush out and not run. Weather can also be a factor...I am sitting in wet and humid...not good painting weather.
All this is assumed you are brushing. If spraying some of this applies but of course there are spraying controls that are also apart of the answer. Key is too much paint being atomized, not moving the gun fast enough, too close...etc.
By the way, when not spraying, I like to use a pad (Woodcraft) or old sock and wipe on the finish...thinned down by 10% or so. And I use very little finish (less chance of running. Adding more coats takes less time than sanding out runs.
Does any of this ring a bell or make sense?
John Lucas www.woodshopdemos.com
I brush from the center of the table towards the outside, not the outside in. that way the heavier portion of the brush-load of material is on the flat part of the table and can be worked towards the edge. Brushing from the edge towards the center builds a heavier coat at the edge that runs over and down.
I'd like to say I figured this out right away, but it took a while...
Hope this is the cause of your problems as it is easy to fix!
Yes I see that is what happened. I used a China brush, but I did go from the end of the table in. Should have thought of that, because when I did my kitchen cabinets I went from the center out. Thanks.