Needing to score 307 to grab a come-from-behind victory after T&T declared their second innings closed on 178-8, Guyana got off to a bright start but slipped to 26-2 at tea after losing Assad Fudadin (02) and Leon Johnson (00) in successive overs.
At that stage with Barnwell on 17 and skipper Travis Dowlin 2, Guyana needed 287 more runs from 39 overs to secure an unlikely win.
After tea, Dowlin was adjudged lbw to Imran Khan for 02, to leave Guyana shakily placed on 31-3 in the third over after the tea break.
The 50 came up in 67 minutes from 17.5 overs with Barnwell contributing 32 of those runs and the in-form Crandon on 12.
Barnwell inched closer to his second half century of the match, when he hoisted a full toss from Samuel Badree over mid off for four to carry his personal score to 40.
He did not get to his second first class 50 of the match, as he offered a catch to Adrian Barath at short leg after the water break, falling for 41 which included six fours and a six off Sherwin Ganga.
The score was then 68-4.
First innings century maker Narsingh Deonarine came to the wicket and immediately struck Amit Jaggernauth through backward square leg for four.
The two took the fight to the Trinidad bowlers with Crandon pulling a delivery from Ravi Rampaul through midwicket for four.
He followed that shot with a drive through mid off as Guyana progressed to 94-4.
The 100 was posted when Crandon hit Jaggernauth over long off for six in the first over of the mandatory 15 overs to be bowled in the final hour.
The 25-year-old Crandon got to his fourth, first-class half century, when he steered Khan past Badree at first slip and down to the third man boundary for his sixth four.
He had faced 73 balls in 110 minutes striking six fours and one six.
Trinidad skipper Daren Ganga seemed desperate to break the partnership and turned to his wicketkeeper Gibran Mohammed, who only ran into a straight drive through mid off for four, from the blade of Deonarine.
When the umpires called off play at 5:19pm Guyana were 133-4, with Crandon on 55 after striking the final delivery of the match from Mohammed for four.
Deonarine was unbeaten on 26 which was decorated with three fours.
Khan (2-33), pollard 1-19 and Sherwin Ganga 1-23 were the wicket takers for T&T in Guyana’s second innings.
Earlier, T&T resumed on 14-1 with Badree (09) and Justin Guillen (1) being the not out batsmen.
They lost Badree, who was run out by Barnwell at backward square and Guillen who played on to Esaun Crandon for 21.
When Khan was dismissed for five Trinidad were 57-4, an overall lead of 185 with six wickets in hand.
Daren Ganga (43) and Kieron Pollard (34) then saw their team to 108-4 at lunch with Ganga on 40 and Pollard 15.
After lunch, Ganga was caught by wicketkeeper Darwin Christian off Steven Jacobs, who also accounted for Pollard in his next over.
The Trinidadians were 140-7 when Barnwell knocked back Sherwin Ganga’s off stump in the fifth over after the lunch break.
Mohammed (17) was adjudged lbw to Jacobs at 164-8, at which point the declaration came.
Ravi Rampaul and Jaggernauth were not out on 20 and three respectively.
Esaun Crandon and Jacobs ended with three wickets each for 31 and 32 runs respectively.