Transposing is a very mechanical process. It's simply understanding a musical alphabet. (ABCDEFG) One must be able to SAY it frontwards and backwards from any point, better than your name, frontwards or backwards, spelling.
Not knowing how you think, this would be the simplest way to approach this view. This excercise can be done on the way to work. ABCDEFG EFGABEDE and so forth. If it's in the mind, the fingers just respond. Notice flats or sharps NEVER deviate from this alphabet. For guitar players, it's just one damn fret. The logic never changes. Please pay attention. Mistakes not only happen in writing, but happen musically. Not a real big deal, when improvising.
Hope this helps?