The procedure is to turn up on your first day in battalion and insist that you are put on all the course you want. The person to approach is the longest serving private in your platoon, preferably one who'se been busted from L/Cpl/ Cpl a few times.
He will make sure your course application is processed.
"In the Inf you" well I hate to be a when I but back in my day the spring cadres used to be used to train internal and external courses for unit specialists such as snipers, assault pioneers, rarden, drivers, mortars, radio and newly in Milan.
Basically if you wanted a specialisation that took you from away from a rifle company then you used to wait about 3 years and a nice support company number came up. Snipers had to be Class 1 soldiers, Marksmen with a real rifle and senior soldiers. No matter what you picked up as B skills on the way during your time, you never were paid extra, never allowed to forget that you were double hatted (our Pioneer pln was basically a section in each rifle coy and never trained together. You were always dicked as coy reserve section which meant piss poor routine in defence. In the Infantry the soldier first saying is the law! Trust me on that. the Yanks we would occaissionally work alongside couldnt understand how we could be infantry and machine gunners and mortar men and well jack of all!
You join, get some time up (ie experience), generally apply to get put on a course for a specialised area (ie mortars course, snipers course etc), then usually if you pass it you'll get put in that unit. Can depend on whether there's vacancys in that area or if theyre short of blokes and need to stab people for it.
you join the Bn once you've finished training, and you will be posted to whatever company is short of manpower at that time (and that could include a support weapons pl) .
You should serve as a rifle pl infantryman for a period of anything from 12 months to 6 years. If you have a talent for a certain job within the Bn you will be expected to attend a cadre run within the Bn. These cadres (as ugly mentions) will be run by the respective experts within the Battalion and will include ALL special to arm infantry courses: mors, snipers, Anti tank recce etc. If you pass the cadre you will then join that platoon.
Simple really but it takes time, training and patience.
Of course if you sign up straight away for the 9 years you will be looked upon favourably and have first refusal for courses, such as driving . And you can also save the difference in pay, so after 3 years you could PVR!