I also find it tricky on grass wickets with spikes to mark it accurately. As i lose the spot i need to mark after asking for middle stump. Any tips guys?
I think I may regret this but...... I'm hoping this is a serious question, so will answer it accordingly (more fool me if not
....)
I usually keep my bat in place and mark behind that using the outer or front pikes until I'm happy, You could also drag your bat a few inches behind to make a better mark first. In all honesty i don't really like using the bat to mark it unless absolutely necessary, but with toe guards on the bottom i am a little less bothered about it now