Since you are discussing braille in your transcription you will want to ensure your mention of contractions will give an accurate description of the sign without causing confusion in the braille-in-braille context.
I think Section 3 of the Rules of UEB should apply in this case:
UEB 3.13.1 Use a dot locator for ‘mention’ to set apart a braille symbol that is <u>under discussion</u>, as in a symbols list, a transcriber's note, or in a <u>publication about braille</u> such as this one. Place the dot locator for "mention" before the braille symbol and unspaced from it.
In your print text, “er” and “ing” should be transcribed uncontracted. The dot locator for “mention” is followed unspaced by the contraction as shown here:
“er” and “ing”
8er0 .=] & 8ing0 .=+
I hope this helps.