Yeah the ones from that link look decent, I just bought small cheap plastic ones, maybe that's why I failed.Thanks for letting me know about those. They look like pretty good quality.
There's a little trick you could apply if you decide to use the funnels- get a bit of thin, not too soft tubing and slide it in the bottle together with funnel. It allows the air to escape from the bottle in case the funnel blocks the entire bottle opening, especially. Any spacer would really work to be honest, doesn't need to be tubing. Didn't really make much difference with the funnels I got, they are simply too small to be used effectively. It would take me forever to get my mixes done- time I don't really want to waste.