ASM coding, do you use a special program, or can you use C for asm-coding instead

If you are only doing fragments, inlining with _asm is the easiest. For anything larger, a dedicated ASM is probably desired.

I recomend looking into RadASM or Asm Studio if you are going to write anything complex and are new to ASM. Coupled with the latest MASM and tutorials and online help, these seem to offer the equiv functionality of a "Visual Studio for ASM".

For patching, though, you can just use Olly and save the EXE. You can even use labels, so for anything less than 30 lines, it can be quite fast. No need to link, no need for a hex editor, or anything.