Been using Butyrate Dope for ... since the 50's... sheeesh!
Butyrate is hot fuel proof so you can fly 1/2a u-control without the tissue falling off mid flight. (an inconvenience...) Thinned 50/50 with pure Acetone from Handy Depot...
I buy SIGSUPERCOAT Butyrate Dope by the quart online, generally 4 quarts at a time as freight is just crippling.
http://www.sigmfg.com/cgi-bin/dpsmart.exe/ProductsV6.html?L+Sig+rzla3485+_Ddp_5fSearch1_02a46PaintSigSuperCDpe_01Search_02Index_01Menu_02CatProd_01Thumb_02Dope_01
specifically:
SIGSD145 SUPERCOAT CLEAR QUART EACH $15.99
50/50 elmers and water does work, but our humidity down here can destroy a project fast, so back to dope, for us...
On the big planes it's cotton muslin fabric, (like an unshrunk bedsheet) shrunk and sealed with 50/50 laquer and laquer thinner...