Start by rolling the arms around a pinpoint position. Both wrists of both people meet at the same spot, and whoever dominates this spot tends to come out on top in the bigger fight.
If you feel your training partner is putting too much weight on your arms, or tensing up a bit, you can exploit this by pulling his tense arm and deflecting his heavy hands.
You can practice this for decades and still have more to learn. Most of the world's best masters are elderly. Sticking Hands is about sensitivity and quick reactions. Excess muscle is a disadvantage.
In the first two videos, see Grandmaster Samuel Kwok sticking hands with his main teacher of recent years, Grandmaster Ip Ching. Ip Ching is the younger son of Ip Man, who had students including Bruce Lee. Sam has also trained for decades under Ip Chun, the elder son of Ip Man.
In the third video, see Ip Chun coaching movie star Donnie Yen in preparation of acting in the Ip Man movie trilogy.
If you're prepared to travel around the UK to train with the best pair of hands you can find, you probably can't do much better than traveling to Blackpool for practice with Grandmaster Samuel Kwok. Although Sam teaches general Wing Chun Kung Fu quite differently to how I would teach it, I have no hesitation to recommend training with him for the purpose of practicing sticky hands. In just a 2 or 3 hour train trip to Blackpool from Birmingham, you can train with one of the world's most thoroughly experienced Chi Sao grandmasters.
Grandmaster Samuel Kwok has kung fu schools all over the world, but lives in Blackpool (UK), and I've been training with him for a few years now.
Consider travelling to Blackpool for some Sticking Hands private tuition with Grandmaster Samuel Kwok. Visit his website: www.kwokwingchun.co.uk
The general Wing Chun of Sifu (Master) Shaun Rawcliffe is also quite different to my own, but his sticking hands technique is highly refined so he is well worth practicing with if you get the opportunity. Shaun Rawcliffe's local Wing Chun club, Midlands Wing Chun Kuen (MWCK), is based in Birmingham and I trained there for a few years myself. But what I actually recommend is simply private lessons, if available.
Visit the website of Master Shaun Rawcliffe: www.wingchun.co.uk
Sticking Hands is also commonly known as: