I've always used the liquid and not the gel. It may act differently and of course we all have different experiences when we color these parts and our situations (prep, climate and so on...) can differ.
For me I've always found that by applying with steel wool the toning is lighter though with multiple applications it can get darker as if the coloring starts reacting with the steel in the steel wool before the part I'm trying to color. Instead I've just found that using a sponge or rag colors quicker for me. Of course small parts, bolts and nuts I simply slosh around in a small cup if I'm going for P&O or for fresh steel its back to the steel wool and burnishing the bends if its sheet metal or stamped steel