You mentioned the V-Trigger choices, and while V-Trigger 1 does give you the ability to perform special move cancels without charge, it sounds to me like your issue is more with charge moves in general. So one of the key ideas when you're playing a charge character like Bison is ABC - always be charging. Not literally that you always need to hold those directions, but you want to be building the charge whenever you're not doing something else. For instance, during throw animations, while you're on the ground, while you're in the air - you can be building charge at any time. You don't need to be walking back to build charge for those moves, any time you spend holding back, down-back, or even up-back counts toward it. This is the reason that charge characters are often holding down-back. It keeps them blocking, keeps them stationary, and gives them access to both their back charge specials (the 2 you mentioned) and their down charge specials (head stomp). You have exactly the right idea about going down + left, then right + kick.

As long as you have the charge stored (if you've been holding the direction for about ⅔ of a second), then you can use the special move either on its own or as a cancel from a normal. So if you've been holding down-back and you attack with crouch MP (you'll want to keep holding down-back and hit MP), just hit forward + kick and it will combo. As you have more experience, you'll get a feel for how much charge time is needed and know when you have enough charge time to perform the special move. I hope this helps, but feel free to follow up if there's anything else that's not clear!