WAW doesn’t support dual-binding via the in-game menu, so you’ll have to edit your config file manually through:
%localappdata%\Plutonium\storage\t4\players
Open your profile folder (the one with a long number) → open config.cfg in Notepad.
Find the line for your X button — it’ll look like:
bind BUTTON_X "+reload"
or
bind BUTTON_X "+use"
Replace it with:
bind BUTTON_X "+usereload"
That makes X both reload and use — it reloads normally, and interacts when you’re near something usable.