Scouting during assault is difficult, since you are moving and enemy is dug-in. Given the same experience level, enemy WILL spot you first, at least with his size 0 units (MG nests, panzershreck teams, snipers, VBs and so on). Once you are in range, you will be fired at. And the scouts of 4 or 5 men do not really have good chances to survive one or two such events.
This infers a simple strategy. Move under barrage and scout simultaneously with normal squads WHEN ASSAULTING. Squads will be of course spotted at longer distance (size 1), so you can use your scouts a hex or two before them. If your scouts are attacked first, squads will relieve them a little with fire support, if your squads are attacked first, your scouts have very good chance to reveal position of firing units.
Barrage helps the process a lot. It is a must have. You cannot expect to ambush the enemy head-on. Use for it something which does not make craters, as you don't want to hamper the movement of your units, once you discovered the enemy. If you have a tank or SPA support, HIDDEN behind nearest terrain wave or smoke, the complete assault of position would look like this: 1] scouts advance say 4 hexes after creeping barrage of 76 mm field howitzers or something like this, 2] one or two hexes behind them come the assault squads, 3] if possible, something hard hitting is hidden and prepared to attack with your infantry in one or at most two turns. You may want to separate enemy discovered enemy position by dropping a smoke BEHIND it, to insure zero damage from possible undiscovered AT gun line etc.
Note on barrage: it seems to me, after some testing, that there are two major factors causing suppresion. First and more important is number of shells landing in a hex. Dropping ten or fifteen or more shells in hex almost guarantees enemy retreat/route status, so you can even safely RUN (really, try it) to his position. Of course, you cannot do this all the time, as normally you have rounds for just ten turns. But you can buy more artillery and use half and half. This way you have almost zero casualties. Biggest danger is your own arty (especially if you run) - try to have the fire hexes in LOS of spotter. Repeat - HE kill seems to have NO effect, unless it causes losses. Which is the second factor causing suppression. But under assault, you would have to buy really BIG guns - 203 mm or so (so repeat - to suppress enemy it is better to buy 76 mm than 155 mm gun). And these are pretty slowly firing, thus reducing the suppression from number of shells, making the predictability of the indirect fire pretty low. Moreover they are dangerous to everybody, not only your enemy. I use them though for distant barrage (to route retreating enemies at longer distance from my troops, at least 7 or 8 hexes from scouts) or better independently to destroy something not easily reachable (distant ATG). BTW even if you can drop just five or three shells on hex, you had better to do it. Enemy rate of fire (and consequently the opfire and your losses) decreases (guesstimate) three times the suppression, i.e. if he has suppression 8, his rate of fire will decrease by 24 percent. Compounded with the effect of your supporting fire squads, which add quickly to enemy suppression by firing back at him, you should have no major problem.
Regarding the time spent to advance one hex at a time... This is absolutely not necessary. You know, that enemy cannot be on your half of battlefield, so under smoke or terrain cover you can rush to say hex 52, if the map is 100 hexes wide. If you chose line of advance the enemy expected, you will soon discover him
No need to creep twenty hexes or so.
And yes, you have to look around manually. Even after every opfire. And also try different units to look at suspected directions. But the real point is, that you should use artillery, to put yourself in the advantage. Otherwise the enemy will regularly spot you first, regardless of terrain, as you are moving and he is dug-in (reduced ability to be seen, naturally).
Regards,
badger45