Focus less on the "swordsman" aspect and more on the character's personality and how you can get that across, possibly using the sword as a prop.
I actually have some training in various martial arts, but when I draw my sword-wielding characters, the only time I really think in terms of "how do I depict perfect sword form" is when the character's personality type is "always uses textbook form" to show that they're very serious about doing things properly.
For everyone else, it's all about what showcases the design best and what showcases their personality best. Aggressive characters might be leaning forward and aggressively slashing, prickly characters might be holding the sword up as if to ward away the viewer, anxious ones might have their weight on their back foot in a guard stance, energetic heroes might point with their swords like "let's go!", formal guardian types may have their hand on a sheathed sword while they stand straight, very laid-back characters might lean on their sword like a cane or sling it over their shoulder like they're carrying a heavy piece of lumber.
Rekki is frequently posed with her sword like it's a big baseball bat, because she's energetic and likes getting attention for being the hero, like a sports star. She's also all about power rather than finesse! Sarin meanwhile, the sword is often a barrier. She's usually holding up her arm or sword with some tension in a way that crosses her body, between her and the reader, showing that she's careful and guarded.
Make it all about using the sword to tell us "who is this person" and "what is unique and interesting about THIS swordfighter?"