Heat Exchanger Fabrication Question?

In a dilemma about exactly how tubes are stuffed in a multi baffle plate heat exchanger. The half plate baffles are already stitch welded on inside of exchanger pipe. With only a 1/64" clearance in holes for tubes I cannot fathom how one would insert a 35 ft tube thru the full length of a pipe with half baffle plates every 8 ft.. It seems like you would need a broom handle type wood stick aligned thru full length of pipe thru each baffle and then use it as a guide for the tube. I don't know, have you had any experience around heat exchanger fabrication? Appreciate your comments and advice, Robert