Do not use any flux. If not in vacuum try to rub with the apliccator when alloy is hot.

Advantages: it has liquid form even at 15-20 deg. Celsius. As result - you can use it for  contact anywhere without any preparation.

Disadvantages: it is not solid at room temperatures. As result - you can create contact but you can't define it's area. Any random additional friction, pressure and so on may change contact area. Also remember that InGa is toxic.

So, if you want to create temporary contact for test measure - use it. If you need in stable high-quality contact - use something else.

Adding to the colleagues above, you can use such Ga In alloy to build micro contacts by injecting it by a syringe as it is liquid at room temperature. For more information please follow the link:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4231928/

wish you success

Thank you very much Dr. Zimmerman, Dr.Abdelhalim and Shynkarenko  for your valuable inputs.