Are there any common exersices for maha mudra. I find it very difficult to bend my body in some asanas, and in general doing all sorts of asanas is very hard for me.
Let me save you time and irreversible damage. Maha mudra or any of the kriya practices and asanas are not to be tried physically. none of them yield. You do not need to trust me - just see at anyone who claims being able to practice them. all of them are ageing faster if anything. No elixir, nothing. Asana's are supposed to "occur" and "happen" when specific channels open.
I have been one of the western revolt-er feeling like a teacher is no mandatory, and I can do it myself, and that was 10 years ago. Mahamudra or any related practices thereoff, come after pranayama. Pranayama is simple you say - not so much. The actual pranayama is a grace-gift. a guru has to give it.
now i said the dreaded word guru. where will you find one, and what if you get cheated, even worse what if u end up getting some useless unaccomplished guru, and practice for a decade for nothing ?
Here, siddanta is important. Trust in your fate and more importantly "courage" to accept your fate, even if it means failures and fake gurus. All we can do is pray. seek truth by heart, and your karma starts to burn. make truth your true desire and all sorts of things start to happen. somewhere along the way - guru will appear.
PS: Currently practising Kriya after hurting myself, following all sorts of crazies from western yoga - which is more of aerobics and body exercise to revoltists yoga groups like https://www.actualized.org etc .. tried various pranayamas myself, various asanas and even mahamudra, imbalanced a whole lot of things, got anxiety etc.. then 6 years back, tried to power-through further and slowly force-slit the tongue to achieve kechari, at some point by some good fortune realized i am causing great harm to myself, started stabilizing and living simple life and being good - but a deep yearning in heart started - a cry for help, and finally now got initiation and practice into kriya- Now i am able to see what a blunder i did. Hope you don't do such things. .. but whatever you choose I wish you well. good luck.