First off getting yourself developed so you can see hear and experience the gods, spirits, and demons is most important.
I provide this meditation for this purpose here
I love working with the Hindu pantheon also. I find that Hinduism works wonderfully in the LHP. The systems merge perfectly really.
Without a sigil or enn, or mantra, the next best thing is a statue or painting of the god, often simply calling the name of the god is enough. The thing about spirits is if you call then they will come. The main thing is that you develop the proper skills to communicate with the spirits. Cheers and good luck!