Alchometer should only be like $20 USD, though if you wanna just use taste, that absolutely works too! I did that with my watermelon brandy (accidentally sat on my alchometer during distillation lol) for the paper towel vs lid or stopper, paper towel is far more permeable to volatile compounds. Could you get away without doing it? Yeah probably. Does it make a difference? Honestly, maybe, maybe not, theoretically to me it makes sense so I’ve done it every time, but I haven’t read any research papers on the topic. But letting it “air out” and let the more volatile stuff out (without letting bugs or fruit flies in) makes sense to me so I do it haha