Originally Posted by Joe Spear
First of all, are you using the gel stain when it's 40 degrees? It may be very stiff. Second, if you're getting "little balls" of it, that sounds like it has already started to cure in the can. You mixed it? Was there a hard layer on the top of the can that you tried to mix in. That would leave little pieces in the stuff that would make "little balls." Third, you shouldn't have to mix gel stain. Just brush it or wipe it on the way it comes from the can with a lint-free rag, and not too thick.
About the shiny spots on the poplar, did you sand thoroughly with 180 to 220 grit before you stained? Or did you sand with a lot finer grit? If so, parts of the wood may be glazed or too smooth to absorb the stain. I would sand the whole thing again with 180-grit sandpaper and restain. I think that if you just put on the poly, the spots might show through, unless you put on 10 coats so that it looked like plastic.
Don't worry about wiping off 75% of the stain. Just put on a coat, wait a few minutes, and wipe. Then after 8 hours or so, wipe on another coat. Repeat again if necessary until you get the tone you want. You might also want to try aniline dyes. With some experimentation of the wood you are using (cut-off scraps, of course), you can control the color real well.