Reb Zeira says (114b, quarter down, as explained by Rashi) that Kohanim don't need tekios for them to work out that one must not be makriv the Chelvei Yom Kippur on Shabbos, as they are Zerizim, Rashi explains experts and they know this already. The Gemoro then asks if they are zerizim, why do they need the tekios every Fri?
I find this question surprising - even if they are experts to know halochos without tekios as a hint, they may still require tekios so they don't lose track of time!
Meir Eliezer Bergman
Manchester UK
Your question can be answered by looking closely at Rashi on 20a (DH Evarim). Rashi writes that the Kohanim are all Bnei Torah and Charedim. Rashi adds that they also remember ("Nizkarim") what they are doing and therefore one may light the bonfire, before Shabbos enters, in the Beis ha'Moked where the Kohanim warm themselves and there is no concern that they might stoke the coals after Shabbos enters.
We learn from Rashi that not only do the Kohanim know the Halachos, but they are also efficient at putting them into practice. Similarly, on Friday afternoon the Kohanim pay close attention to the time and remember that Shabbos is coming in soon and therefore they do not require the Teki'os on Erev Shabbos which are necessary only for the other people in Yerushalayim.
Apologies for the delay in replying to this question.
Kol Tuv,
Dovid Bloom