In general, by step, I think everything is clear, the work is not difficult, but requires a certain skill. Advice:
1 - print directly the size of which will be final for your crafting.
2 - Do not use aerosol paint, corrodes polyester even through primer paint.
3 - for gluing better glue on a rubber base.
4 - I cut with a stationary knife, but this is convenient only in areas requiring extreme accuracy, in other cases, it is better to use an angle grinder.
Primer • Glue • Polyester • Clerical knife • Angel grinder • Set of acrylic paints
Step1 - finddraw an image of your future craft.
Step 2 - draw a contour on a sheet of expanded polystyrene.
Step 3,4,5 - cut all elements, form them and glue them together.
Step6 - paint the result according to the official arts/character.
Kindred`s bow - result.
That`s how I looked on the festival)
Group photo of my cosplay band - blade looks nice.