Trailing 18-6 with an hour played at the Stoop, Gentle's charges looked on course for defeat before tries from Joe Westerman and Richard Horne - both converted by Danny Tickle - secured an unlikely draw.
And Gentle has urged his team to show the same freedom from the start going forward rather than waiting until they are chasing the game. He said: "We're still, for some reason, playing very conservatively. We're not doing a lot of things which we work on during the week."
Gentle added: "It wasn't until we started to chase points that we threw the ball around, started getting some shape and grew in confidence. I don't know whether it's a lack of self-belief, or just trying to hang in with sides at the moment but we've got to get to the bottom of it.
"It took us a long time to warm into the game. It was just horrible conditions, and a horrible game really. A draw is probably a good result. I'm happy with a point. Look, these conditions are horrendous to play in so we'll take the point. We've got a few players missing but we'll make do over the next few weeks."
The Broncos had looked set to secure only a third win of the Super League campaign after tries from Tommy Lee, Kieran Dixon and Matt Cook established a dominant lead, with head coach Tony Rea admitting conceding so late was difficult to take.
"It's hard to say we're happy with a point," he said. "It doesn't feel like a win, having been in front for a large part of the game. Having said that, we left nothing out there and the spirit of the team along with the enthusiasm and the effort was everything you want to see.
"I'm only disappointed because Hull scored a last-minute try, and it's then that you start feeling like we should have won. It was a contest from start to finish with both teams fighting all the way.
"We were untidy in bits, and they were untidy in bits. It was just the back-end of the match that didn't go our way.
"We didn't have Craig Gower as he had a groin issue from last week. If he was fit he would have played, but he should be back for our Easter games."
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- Joe Westerman