Everyone should be usng a TDS meter to determine nute strength. If not then it's a crap shoot to determine the correct ratio every time. The same with PH. If your not checking your PH your taking chances of over or underferting as the PH determines a plants ability to uptake nutrients. Saying this...full strength bloom nutes or the proper mix should be as easy to obtain as full strength veg ferts were.
To the OP...I'd go to bloom nutes when I go 12/12. No reason to to wait a week unless your plants are nitrogen deficient and need the extra N.
Or you have not gotten your ph or TDS meter like me, then you have to do it all by look and feel Not the best way to do it, no. That's just the way I do it to ensure I don't over fert. If I do over do the nutes, it's only by a little bit, and it's manageable.
But when I started my grow, I had no money to spend, so I had to make do.
Oh don't get me wrong my friend. I can understand 100% how hard it is to aquire equipment when first starting out. I started indoors with 4foot shop lights and bathroom and PC fans.lol I now have a enviromental controller, light mover, 1000watt hps 8" elicent fan and tons of extra. Plus all the meters I need. It takes time but IMO one of the first things one should buy are a TDS meter and PH kit. Then a good fan is next IMO. If you can't control the plants nutrient and enviroment you won't have a very good grow. Ph kits are super cheap and TDS meters can be bought for almost nothing these days. I picked one up off ebay for $10.00 and saw a ebay store that sell RO set ups selling TDS meters for $35.00 or so. Fans on the other hand are extremely expensive. I got lucky and found one on ebay being sold buy someone who didn't research the value. My fan goes for over 250.00 retail and I got it for $150.00 ater shipping.
I understand the need for cheapness. I don't agree that one should stay cheap though. As one goes on and doesn't have to spend money on meds or smoke one should be able to put money towards equipment and supplies. Isn't the idea to get as much as possible from your grow? Well cheap doesn't do that. Trust me. I've been there and done that. The only way cheap pays off is outside.
To tell you the truth...while I stress meters and doing things right...I'm truly for what ever works for you. Getting meds is what it's all about and if that means you use floros and shoe strings then that's what you use.lol I'll never knock ingenuity or handiness when it comes to growing. I know where I started and it wasn't with anything near what I have now.