So you have to have a rigorous scan: horizon, balance ball, horizon, ASI, horizon, altimeter, horizon, DI, horizon, altimeter, horizon... etc.
For goodness sake. Steep turns are a visual manoeuver - you are not flying on instruments.
Everyone seems to forget these days you are flying the aircraft by visual reference - learn to do that well first. To do so you don’t need any of these instruments, they will only make the job harder.
Why do you never do steep turns in IMC? -because even if your instrument flying is very good, you are chasing the instruments.
Learn to do it visually, even if it takes a lot longer, because you will develop a proper feel of the aircraft, you will know where the aircraft should be to maintain 40, 50 or 60 degrees of bank, and you will know whether or not you are climbing.
In short maintain the correct attitude as has already been said and you will execute a good steep turn.